Sheet Pan Strawberry Pop Tart Bars (Sourdough)
These sheet pan strawberry pop tart bars have a flaky sourdough pastry crust, thick cooked strawberry filling, and sprinkle icing.
Servings: 12 Bars
Calories: 350kcal
Equipment
- 13x9 quarter sheet pan
- Parchment paper
- Large mixing bowl
- Medium saucepan
- Pastry cutter
- Rolling Pin
- kitchen scale
- plastic wrap
- - Pastry brush
- Offset spatula
- Wire cooling rack
- Sharp knife
Ingredients
PASTRY DOUGH
- 300 grams all purpose flour 2 1/2 cups
- 226 grams unsalted butter cold and cubed (1 cup / 2 sticks)
- 75 grams sourdough discard or active starter cold (1/3 cup)
- 75 grams ice water 5 tablespoons
- 12 grams granulated sugar 1 tablespoon
- 6 grams fine sea salt 1 teaspoon
STRAWBERRY FILLING
- 500 grams fresh or frozen strawberries thawed and drained if frozen, roughly chopped (about 3 cups)
- 65 grams granulated sugar 1/3 cup
- 24 grams cornstarch 3 tablespoons
- 10 grams lemon juice 2 teaspoons
- 5 grams vanilla extract 1 teaspoon
EGG WASH
- 1 large egg
- 15 grams whole milk 1 tablespoon
ICING
- 180 grams powdered sugar sifted (1 1/2 cups)
- 30 grams heavy cream 2 tablespoons, plus more by the teaspoon if needed
- 5 grams vanilla extract 1 teaspoon
- 1 small pinch fine sea salt
- rainbow sprinkles for top, optional
Instructions
MAKE THE FILLING
- Whisk the cornstarch and sugar together dry in a medium saucepan before adding anything else. Mixing them dry first prevents the cornstarch from clumping when it hits liquid.
- Add the strawberries, lemon juice, and vanilla to the saucepan and stir to combine.
- Cook over medium heat, stirring frequently but gently, until the mixture comes to a full boil and thickens noticeably, about 8 to 10 minutes. The filling must reach a full boil to activate the cornstarch properly.
- Transfer the filling to a bowl and press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate until completely cold, at least 1 hour. The filling will firm up significantly as it cools, which is exactly what you want for clean cuts.
MAKE THE DOUGH
- Whisk the flour, sugar, and salt together in a large mixing bowl.
- Add the cold cubed butter and use a pastry cutter to work it into the flour until the mixture looks like rough, uneven crumbles with butter pieces ranging from pea sized to almond sized. Do not overwork. Visible butter pieces are what create the flaky layers during baking.
- Place the entire bowl in the freezer for 10 minutes. This step firms the butter back up after working it in, without the frustration of starting with frozen butter.
- Whisk the cold sourdough discard/starter and cold water together in a small bowl until combined. Pour the liquid over the chilled flour and butter mixture and use a fork to toss until the dough comes together in shaggy clumps. If the dough is still too dry to hold together when pressed, add ice water one teaspoon at a time to the crumbs that are dry
- Divide the dough in half and press each half into a flat rectangle. Wrap tightly in plastic wrap and refrigerate for at least 2 hours or up to 3 days.
ROLL AND ASSEMBLE
- Preheat the oven to 375 degrees F. Line the quarter sheet pan with parchment paper leaving overhang on all sides. The overhang makes it easy to lift the finished slab out of the pan.
- Remove one dough rectangle from the refrigerator and let it sit at room temperature for 10 minutes before rolling. Do not skip this rest or the dough will crack, and do not let it sit longer than 10 minutes or the butter will soften too much.
- Place the dough between two sheets of parchment paper and roll it out to a rectangle slightly larger than the pan, about 14 by 10 inches. (Or use a lightly flour dusted surface) Transfer to the prepared pan and press it into the corners and up the sides slightly. This creates a natural border that helps contain the filling.
- Spread the cold strawberry filling evenly over the bottom layer, leaving a 1/4-1/2 inch border on all sides.
- Roll the second dough rectangle to the same size between parchment paper. Lay it over the filling and press the edges down firmly with your fingers to create a seal all the way around.
- Whisk the egg and milk together and brush generously over the entire top surface. Poking vent holes with a fork or skewer across the top is essential. Without them, steam forces its way out through the sealed edges and causes the filling to leak.
BAKE
- Bake for 30 to 35 minutes, checking at the 25 minute mark since all ovens vary. The top should be deep golden brown, much darker than you might expect. A pale top means an underbaked bottom layer.
- Let the bars cool for about an hour in the pan on a wire rack before glazing. Then carefully transfer to the wire rack without the pan. i place a cutting board on top and gently flip, so the poptart is upside down. Then place the cooling rack on top and fip again. Making the top free and the bottom resting on the wire cooling rack. Cool completely. Do not rush this step. Glazing warm bars will cause the icing to run and will not set properly.
GLAZE AND CUT
- Sift the powdered sugar into a bowl. Add the vanilla and salt, then add the heavy cream starting with 2 tablespoons, whisking after each addition. The icing should move slowly off a spoon like honey. If it is too thick, add more cream one teaspoon at a time.
- Pour the icing over the completely cooled bars and spread quickly to the edges with an offset spatula. Add the sprinkles immediately before the icing begins to set.
- Let the icing set for at least 1 hour at room temperature. It should be dry and firm to the touch before cutting.
- Cut 3 columns by 4 rows for 12 bars using a sharp knife or pizza cutter. Wipe the blade clean between each cut for the cleanest edges. Bars cut best cold, straight from the refrigerator.
Notes
Storage:
Store the bars uncovered in the refrigerator for up to 3 days. Do not wrap in plastic wrap as trapped moisture will soften the icing and top crust. For longer storage, freeze individual bars in a single layer on a parchment lined sheet, then transfer to a zip top bag for up to 2 months. Thaw in the refrigerator overnight.
Make Ahead:
This recipe is well suited to making ahead. The strawberry filling can be made up to 3 days in advance and refrigerated. The pastry dough can be made up to 3 days in advance and refrigerated. The fully assembled unbaked slab can be refrigerated overnight before baking. The fully baked and glazed bars store well in the refrigerator for up to 3 days.
Starter Options:
Discard: use straight from the refrigerator, cold. No adjustments needed. Active starter: works the same way. Make sure it is cold before adding to keep the butter from warming up. Long ferment: after dividing and wrapping the dough, refrigerate overnight or up to 3 days. The extended fermentation adds subtle flavor complexity and makes the dough noticeably more relaxed and easier to roll. This is the recommended approach if your schedule allows.
Frozen Strawberry Note:
Thaw frozen strawberries completely and drain off the excess liquid before cooking. Do not add them straight from frozen. Frozen strawberries release a significant amount of water as they cook, which dilutes the filling and prevents it from setting firmly enough to cut clean bars. To thaw quickly, place in a microwave safe bowl and microwave in 30 second intervals, stirring between each, until fully thawed. Usually 2 to 3 rounds. Drain in a colander and press gently before chopping.
Store Bought Jam Shortcut:
Store bought strawberry jam works in a pinch. Choose a jam where strawberries are the first ingredient and the ingredient list is short. Stir 1 tablespoon of cornstarch mixed with 1 tablespoon of cold water into the jam in a small saucepan. Bring to a boil over medium heat and simmer for 2 minutes, stirring constantly. Cool completely before spreading. You will need approximately 1 cup of jam.
Fat Substitutions:
Palm oil shortening can be substituted for the butter at a 1 to 1 ratio by weight. The crust will be slightly less flavorful and will not brown as deeply. Use it cold, the same way you would use cold butter. You may need to add a teaspoon or two of additional ice water to compensate since shortening contains no water. Lard can also be substituted at a 1 to 1 ratio by weight and produces a notably tender, flaky result. The same additional water note applies.
Gluten Free Option:
Substitute a measure for measure gluten free all purpose flour blend at the same weight. The dough may feel slightly more fragile than a traditional pastry dough. Handle gently and use the parchment paper rolling method to transfer without tearing. You may need a teaspoon or two of additional ice water as gluten free flour blends absorb liquid differently.
Tips for Clean Cuts:
The filling must be fully cold before assembly. Warm filling melts the butter before baking and leads to a soggy bottom layer. Do not skip the full boil on the filling. Undercooked cornstarch will not set and the filling will run when cut. Let the bars cool completely before glazing and again after glazing before cutting. A cold bar cuts cleaner than a room temperature bar. Refrigerate after glazing and cut straight from the refrigerator for the best results.
Troubleshooting:
Dough cracking when rolling: Let the dough sit at room temperature for the full 10 minutes before rolling. Press cracks back together with your fingers and continue. Filling leaking at the edges: The border was too small, the seal was not pressed firmly enough, or there were not enough vent holes in the top crust. Steam needs somewhere to escape. Pale top crust: The bars needed more time. Deep golden brown is the target color. Check at 25 minutes but do not pull them early. Icing too thick to spread: Add heavy cream one teaspoon at a time until it reaches a slow honey consistency.
