Lemon Blueberry Crumble Cookies
Soft, buttery lemon cookies with jammy blueberries and crispy crumble topping. The upside down baking method prevents bleeding berries and creates a completely unique cookie you won’t find anywhere else.
Calories: 290kcal
Equipment
- 2.5 to 3 inch circle cutter or wide mouth canning jar
- Large baking sheet
- Parchment paper
- Rolling Pin
- Medium saucepan
- Small bowl for cornstarch slurry
- Thin flexible spatula or offset spatula
- Microplane or zester
- Food processor (optional, for crumble)
- Mixing bowls
- Whisk
- plastic wrap
Ingredients
Sourdough Cookie Base
- 120 g active sourdough starter 1/2 cup
- 113 g unsalted butter softened (1/2 cup)
- 80 g powdered sugar 2/3 cup
- 67 g brown sugar packed (1/3 cup)
- 50 g egg 1 large egg
- 5 g vanilla extract 1 teaspoon
- 1 tablespoon lemon zest from about 1 large lemon
- 270 g all-purpose flour 2 1/4 cups
- 2 g baking powder 1/2 teaspoon
- 1.5 g salt 1/4 teaspoon
- 1/8 teaspoon cream of tartar
Fermented Lemon Crumble
- 120 g all-purpose flour 1 cup
- 80 g brown sugar packed (1/3 cup)
- 30 g powdered sugar 1/4 cup
- 2.5 g salt 1/2 teaspoon
- 1 teaspoon lemon zest
- 30 g active sourdough starter 2 tablespoons
- 60 g cold unsalted butter cubed (1/4 cup)
- 2.5 g vanilla extract 1/2 teaspoon
- 10 g fresh lemon juice 2 teaspoons
Lemon Blueberry Compote
- 450 g fresh or frozen blueberries 3 cups
- 60 g granulated sugar 1/4 cup
- 24 g cornstarch 3 tablespoons
- 25 g fresh lemon juice 1 tablespoon plus 2 teaspoons
- 1 teaspoon lemon zest
Lemon White Chocolate Drizzle
- 100 g white chocolate finely chopped (about 3/4 cup)
- 1 to 2 teaspoons coconut oil
- 1/4 to 1/2 teaspoon lemon extract
- 1 teaspoon lemon zest
Instructions
Prepare Dough and Crumble for Fermentation
- Make the lemon cookie dough.
- In a large bowl, cream together softened butter, powdered sugar, and brown sugar until light and fluffy.
- Add egg and vanilla extract. Mix well.
- Add sourdough starter and lemon zest. Mix until combined.
- In a separate bowl, whisk together flour, baking powder, salt, and cream of tartar.
- Gradually add dry ingredients to wet ingredients, mixing until just combined.
- Wrap dough in plastic and refrigerate for 12 to 24 hours.
- Make the fermented lemon crumble (Hand Method).
- In a medium bowl, mix flour, brown sugar, salt, powdered sugar, lemon zest, and sourdough starter.
- Add cold cubed butter and cut in using a pastry cutter or your fingers until mixture resembles coarse crumbs.
- Add vanilla and lemon juice. Mix gently until just incorporated.
- Cover bowl and refrigerate alongside the cookie dough for 12 to 24 hours.
- Make the fermented lemon crumble (Food Processor Method - Easier).
- Add flour, brown sugar, salt, powdered sugar, lemon zest, and sourdough starter to food processor.
- Pulse 3 to 4 times to combine dry ingredients.
- Add cold cubed butter and pulse 10 to 15 times in short bursts until mixture resembles coarse crumbs.
- Add vanilla and lemon juice. Pulse to incorporate. Youre looking for a brown sugar texture. You should be able to take some in your hand and squeeze it and it stays together, but be able to break it back apart.
- Transfer to a bowl, cover, and refrigerate alongside the cookie dough for 12 to 24 hours.
Assembly and Baking
- Prepare the lemon blueberry compote.
- In a small bowl, whisk together cornstarch and lemon juice until smooth to create a slurry.
- In a medium saucepan, combine blueberries, granulated sugar, and lemon zest.
- Cook over medium heat, stirring gently, for 5 to 7 minutes until blueberries begin to burst and release their juices.
- Spoon a few spoonfuls of the hot blueberry liquid into the cornstarch slurry, whisking constantly to temper it.
- Pour the tempered cornstarch slurry back into the saucepan with the blueberries.
- Continue cooking, stirring gently, for 2 to 3 more minutes until mixture thickens and becomes glossy.
- Remove from heat and let cool completely for at least 30 minutes.
- Prepare for assembly.
- Preheat oven to 350°F (175°C).
- Line a large baking sheet with parchment paper.
- Get your 2.5 to 3 inch circle cutter or wide mouth canning jar ready.
- Assemble the cookies.
- Using your circle cutter as a guide, spread about 2 rounded tablespoons of fermented lemon crumble directly on the parchment in circles. Space them about 2 inches apart.
- If you want a beautiful marbled top, leave little spots and gaps in the crumble where the compote can touch the pan directly. This creates gorgeous color peek through between the crumble after baking.
- Top each crumble circle with a tablespoon of cooled lemon blueberry compote. Gently spread, leaving a little border.
- Roll out the fermented lemon cookie dough on a well floured surface to a rough rectangle, approximately 13”x 12”, about 3/8” inch thick.
- Using your circle cutter, cut out circles from the dough.
- Gently gather scraps, press together to form another rectangle, and continue cutting until all dough is used. If the dough becomes resistant, wrap well and place in the fridge for 15-30 minutes to allow the gluten to relax.
- Place each cookie circle on top of the crumble and blueberry layers.
- Gently press down to adhere, making sure the crumble and blueberry compote are underneath the cookie.
- Bake the Cookies
- Bake for 18 to 23 minutes, until cookie tops are golden brown and set. You should see browning on the bottom edges.
- Remove from oven and let cool on the baking sheet for at least 1 hour. This is crucial for the compote to set properly.
- Once cool, use a thin flexible spatula to carefully flip each cookie over so the crumble is on top.
- Add lemon white chocolate drizzle.
- Melt white chocolate with coconut oil in a microwave (stirring every 20 seconds) or in a double boiler until smooth.
- Add lemon extract and stir well to combine.
- Fold in lemon zest.
- Using a spoon or piping bag, drizzle the lemon white chocolate over the cooled cookies in a zigzag pattern.
- Let chocolate set for about 30 minutes at room temperature before serving.
- Serve and store.
- Serve immediately or store covered at room temperature for up to 3 days.
- Refrigerate after 3 days for up to 5 days total.
Notes
Gentle Handling and Cooling (Critical):
Let cookies cool on the baking sheet for at least 1 hour before flipping. The cornstarch in the blueberry compote continues to thicken and set as it cools, transforming from a liquid to a stable, jammy layer. Moving the cookies too early will cause them to fall apart. Use a thin, flexible spatula and work slowly, supporting the entire cookie as you turn it over.
Storage:
Store cookies in an airtight container at room temperature for up to 3 days. After 3 days, refrigerate for up to 5 days total. The texture stays soft and tender thanks to the moisture from the blueberries and the fermented dough. The crumble will soften slightly in the refrigerator but the cookies remain delicious.
Quick Turnaround Option (2 Hours):
You can make these cookies in as little as 2 hours if you skip the long fermentation. Make the compote first and refrigerate to cool quickly. Mix your cookie dough and crumble, then chill both. For faster chilling, press your mixed cookie dough into a wide, flat disc on a plastic wrap lined counter, wrap it up, and refrigerate. The flatter shape chills much faster than a thick block. Once the dough is cold enough to roll, assemble and bake. The cookies will be delicious, just without the added depth that fermentation brings.
Make Ahead Options:
Option 1: Mix your dough and make your compote in the evening. Refrigerate everything overnight. The next morning, roll out your dough, assemble, and bake.
Option 2: Mix everything, roll out your dough and cut your circles, make your compote, and refrigerate all components separately overnight. The next day, just assemble and bake. This is the fastest day-of assembly process.
The blueberry compote can be made up to 3 days ahead and stored in the refrigerator. Bring it to room temperature before assembly so it spreads easily.
Substitutions:
Fresh or Frozen Blueberries: Frozen wild blueberries have a more concentrated blueberry flavor and work beautifully here. Fresh blueberries taste equally delicious. If using frozen, add them straight from frozen without thawing and cook the compote a bit longer to reach the right thickness.
Different Berries: Raspberries, blackberries, or a mixed berry blend all work with the same method. Adjust the sugar in the compote based on how sweet or tart your berries are. Raspberries are more tart and may need an extra tablespoon of sugar.
Dairy Free: Plant based butter can be substituted, though I have not tested it myself. The texture may vary slightly. If you try it, let me know how it goes in the comments.
Non-Sourdough Option: Replace the 120 g starter in the cookie dough with 60 g flour and 60 g milk. Replace the 30 g starter in the crumble with 15 g flour and 15 g milk. Skip the long fermentation and chill the dough for 2 hours before rolling. The cookies will still be good, just without the tender texture and depth that fermentation provides.
Tips for Success:
Dough Thickness: Rolling to exactly 3/8 inch thick matters here. Too thin and the cookie overbakes, too thick and it stays doughy in the center. Use a ruler if you are unsure.
Fresh Lemon is Essential: Bottled lemon juice will not give you the bright, vibrant flavor that makes these cookies special. Always use fresh squeezed lemon juice and freshly zested lemon.
Cold Butter for Crumble: If your butter warms up while you are making the crumble, refrigerate the whole mixture for 10 minutes before continuing. Cold butter is what creates the best crumble texture.
Marble Top Technique: When spreading crumble circles onto the parchment, leave small gaps and spots where the compote can touch the pan directly. This lets the blueberry color peek through between the crumble pieces after baking for a beautiful marbled effect.
Fermentation Sweet Spot: 12-24 hours of fermentation in both the dough and crumble delivers the best flavor and the most tender texture.
Troubleshooting:
Cookies Fell Apart When Flipped: They needed more cooling time. Give them the full hour on the baking sheet before flipping. The compote has to fully set or the cookies will not hold together.
Compote Did Not Thicken: Make sure you used cornstarch and not flour. Cook until the mixture is visibly thick and glossy. It will continue setting as it cools, so do not panic if it still seems loose right off the heat.
Crumble Too Dense After Baking: The butter was likely too warm when mixed, or the crumble was overworked. Keep the butter cold and handle the mixture gently. It should look like coarse, damp sand before it goes into the refrigerator.
Cookies Spread Too Much: Your butter may have been too soft when you mixed the dough, or the dough was not fully chilled before baking. Make sure dough is cold when it goes into the oven. If your starter is very wet, you can add an extra 2 tablespoons of flour to the dough.
White Chocolate Drizzle Too Thick: Add more coconut oil a few drops at a time until it reaches a drizzleable consistency.
White Chocolate Drizzle Too Thin: Let it sit for 1 to 2 minutes to cool slightly. White chocolate thickens quickly as it cools.
