Day 1: Prepare Dough and Crumble for Fermentation

Make the Cookie Dough

• In a large bowl, cream together softened butter, powdered sugar, and brown sugar until light and fluffy.
• Add egg, vanilla extract, and almond extract (if using), mix well.
• Add sourdough starter and 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 in plastic and refrigerate for 12-24 hours.

Make the Fermented Crumble (Hand Method)

• In a medium bowl, mix flour, brown sugar, salt, powdered sugar, cinnamon, 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 mix gently.
• Cover and refrigerate alongside the cookie dough for 12-24 hours.

Make the Fermented Crumble (Food Processor Method, my favorite)

• Add flour, brown sugar, salt, powdered sugar, cinnamon, and sourdough starter to food processor.
• Pulse 3 to 4 times to combine dry ingredients.
• Add cold cubed butter and pulse 10-15 times in short bursts until mixture resembles coarse crumbs.
• Add vanilla and pulse 1-2 times just to incorporate.
• Pulse until all ingredients combine and you have a brown sugar type texture to your crumble. Go slowly—you don’t want it to turn into a dough.
• Cover and refrigerate alongside the cookie dough for 12-24 hours.

Day 2: Assembly and Baking

Prepare the Peach Pie Filling

• Cut 4 medium peaches in half and remove pits.
• Place cut-side down on a parchment-lined baking sheet.
• Preheat broiler and position rack 6 inches from heat.
• Broil for 1-2 minutes until skins blister slightly.
• Remove and let cool for 1 minute, then peel skins off easily with your fingers.
• Slice peeled peach halves into 1/4-inch thick pieces (325g total).
• In a medium saucepan, combine sliced peaches (fresh or frozen), granulated sugar, cornstarch, lemon juice, vanilla extract, ground ginger, cinnamon, nutmeg, and salt.
• Cook over medium heat, stirring gently, for 10-12 minutes until peaches begin to soften and release their juices. If using frozen, cooking time will be less.
• Continue cooking for 2-3 more minutes until mixture thickens and becomes glossy.
• Most peaches should soften but some can remain slightly firm for texture.
• Remove from heat and let cool completely (at least 45 minutes). Cover with plastic wrap and refrigerate until cold for faster cooling.

Assemble the Cookies

• Preheat oven to 350°F (175°C).
• Line a large baking sheet with parchment paper.
• Using a 2.5-3 inch circle cutter as a guide, spread about 2 rounded tablespoons of fermented crumble mixture on the parchment in circles. Leave small gaps between crumble pieces for a marbled effect.
• Top each crumble circle with 1 tablespoon of cooled peach pie filling, gently spread around the middle. Try to keep it from going over the edges of the crumble.
• Roll out the fermented cookie dough on a floured surface to a rough rectangle, 13 by 12 inches, approximately 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.
• Place each cookie circle on top of the crumble and peach layers.
• Gently press down to adhere making sure the crumble and peach filling are under the cookie.

Bake the Cookies

• Bake for 18-22 minutes, until you can see dark golden browning on the crumble edges.
• Remove from oven and let cool completely on the baking sheet. The peach pie filling will continue to thicken and set as it cools.

Add the White Chocolate Drizzle

• Melt white chocolate with coconut oil in a microwave (mixing every 20 seconds) or double boiler, until smooth.
• Using a spoon or piping bag, drizzle melted white chocolate over the cooled cookies.
• Let chocolate set for about 1 hour before serving.