Blackberry Crumble Bar

How to Make Blackberry Crumble Bar

1. 1

   Step 1: Preheat and prepare pan

   Heat the oven to 350°F (175°C). Line an 8x8-inch (20x20 cm) square pan with parchment, leaving an overhang on two sides for easy removal, and lightly grease the parchment.
2. 2

   Step 2: Mix the oat crumble base

   In a large bowl combine the flour, rolled oats, light brown sugar, baking powder, and pinch of salt. Stir in the melted butter until the mixture holds together in coarse clumps; reserve about 1 1/4 cups of the mixture for the topping and press the remaining mixture firmly and evenly into the prepared pan. Par-bake the base for 10–12 minutes until it just begins to set but is not browned; remove from oven.

   For this step

   • 1 cupall-purpose flour (or gluten-free blend)
   • 1 cupold-fashioned rolled oats
   • 3/4 cuplight brown sugar, loosely packed
   • 1/2 teaspoonbaking powder
   • 1 pinchfine sea salt
   • 1/2 cupunsalted butter, melted
   
3. 3

   Step 3: Cook the blackberry filling

   In a medium saucepan or bowl, gently mash the blackberries with the granulated sugar, cornstarch, and lemon juice until combined but still slightly chunky. Warm over low heat just until the sugar dissolves and the juices thicken slightly (about 2–4 minutes) — you want a glossy, spoonable filling, not a full jam.

   For this step

   • 2 cupsfresh blackberries
   • 1/4 cupgranulated sugar (adjust to taste)
   • 1 tablespooncornstarch
   • 1 tablespoonfreshly squeezed lemon juice
   
4. 4

   Step 4: Assemble and top

   Spread the blackberry filling evenly over the par-baked oat base. Scatter the reserved crumble mixture evenly over the fruit, pressing lightly so the topping adheres to the filling.
   
5. 5

   Step 5: Bake until bubbly and golden

   Return the pan to the oven and bake 25–28 minutes, or until the filling is bubbling at the edges and the topping is golden brown. If the topping browns too quickly, tent loosely with foil for the last 5–10 minutes.
   
6. 6

   Step 6: Cool, remove, and slice

   Let the bars cool completely in the pan (at least 1–2 hours) so the filling sets, then lift them out using the parchment overhang and slice into 8 bars. Store in an airtight container in the refrigerator for up to 4 days or freeze for longer storage.
   

1. Heat the oven to 350°F (175°C). Line an 8x8-inch (20x20 cm) square pan with parchment, leaving an overhang on two sides for easy removal, and lightly grease the parchment.
2. In a large bowl combine the flour, rolled oats, light brown sugar, baking powder, and pinch of salt. Stir in the melted butter until the mixture holds together in coarse clumps; reserve about 1 1/4 cups of the mixture for the topping and press the remaining mixture firmly and evenly into the prepared pan. Par-bake the base for 10–12 minutes until it just begins to set but is not browned; remove from oven.
3. In a medium saucepan or bowl, gently mash the blackberries with the granulated sugar, cornstarch, and lemon juice until combined but still slightly chunky. Warm over low heat just until the sugar dissolves and the juices thicken slightly (about 2–4 minutes) — you want a glossy, spoonable filling, not a full jam.
4. Spread the blackberry filling evenly over the par-baked oat base. Scatter the reserved crumble mixture evenly over the fruit, pressing lightly so the topping adheres to the filling.
5. Return the pan to the oven and bake 25–28 minutes, or until the filling is bubbling at the edges and the topping is golden brown. If the topping browns too quickly, tent loosely with foil for the last 5–10 minutes.
6. Let the bars cool completely in the pan (at least 1–2 hours) so the filling sets, then lift them out using the parchment overhang and slice into 8 bars. Store in an airtight container in the refrigerator for up to 4 days or freeze for longer storage.