Ingredients:

  • 1 ½ cups (192g) all-purpose flour, plus more for dusting
  • ½ cup (100g) granulated sugar
  • ½ teaspoon kosher salt
  • ¾ cup (1 ½ sticks or 170g) unsalted butter, cold and cut into cubes
  • 1 large egg yolk
  • 1 teaspoon lemon zest
  • 4 cups (approx. 400g) fresh blueberries, rinsed and patted dry
  • ¼ cup (50g) granulated sugar
  • 2 tablespoons cornstarch
  • 1 tablespoon lemon juice
  • 1/2 teaspoon lemon zest
  • ½ cup (64g) all-purpose flour
  • ½ cup (50g) rolled oats (not instant)
  • ⅓ cup (67g) packed light brown sugar
  • ¼ teaspoon kosher salt
  • 6 tablespoons (85g) unsalted butter, cold and cut into cubes

Instructions:

  1. Combine flour, sugar, and salt in a bowl. Cut in cold butter until mixture resembles coarse crumbs. Add egg yolk and lemon zest; mix until a dough forms.
  2. Press dough into the prepared baking pan. Prick the crust with a fork. Chill for at least 30 minutes.
  3. Bake the crust in a preheated oven (350°F/175°C) for 15-20 minutes, or until lightly golden. Let cool slightly.
  4. Gently toss blueberries with sugar, cornstarch, lemon juice, and lemon zest.
  5. Combine flour, oats, brown sugar, and salt. Cut in cold butter until mixture is crumbly.
  6. Spread blueberry filling evenly over the partially baked crust. Sprinkle crumble topping evenly over the blueberries.
  7. Bake in the preheated oven for 35-40 minutes, or until the crumble topping is golden brown and the blueberry filling is bubbly.
  8. Let cool completely in the pan before cutting into bars. Lift using the parchment paper overhang.