Ingredients:

  • 2 1/4 cups All-Purpose Flour (Sifted)
  • 1/2 cup Granulated Sugar (for crumble)
  • 1/2 tsp Fine Sea Salt
  • 1 cup (2 sticks) Unsalted Butter, very cold, cut into 1/2-inch cubes
  • 1 Tbsp Lemon Zest
  • 4 Large Eggs, room temperature
  • 1 1/2 cups Granulated Sugar (for filling)
  • 3/4 cup Fresh Lemon Juice
  • 2 Tbsp All-Purpose Flour (for filling stabilizer)
  • 1/2 tsp Baking Powder
  • 2 Tbsp Icing Sugar (Confectioner's Sugar), for dusting

Instructions:

  1. Prep the Oven and Pan: Preheat the oven to 350°F (175°C). Line an 8x8 inch baking pan with parchment paper, leaving generous overhang on two sides for easy removal.
  2. Combine Dry Crumble Ingredients: In a large bowl, combine the flour, sugar (1/2 cup), salt, and lemon zest. Whisk briefly.
  3. Cut in the Butter: Add the cold, cubed butter. Mix until the mixture resembles coarse, pea-sized crumbs. Do not overmix.
  4. Divide and Chill: Reserve 1 cup (about 1/3) of the crumb mixture and place it in the fridge immediately. Press the remaining mixture firmly and evenly into the bottom of the prepared baking pan.
  5. Par-Bake the Base: Bake the pressed base for 18–20 minutes, or until the edges are lightly golden brown. Remove from the oven but leave the oven on.
  6. Whisk the Filling Ingredients: While the base is warm, make the filling. In a separate bowl, lightly whisk the eggs until just combined. Gradually whisk in the sugar (1 1/2 cups) until dissolved.
  7. Add Lemon and Stabilizers: Whisk in the fresh lemon juice, then gently fold in the 2 tablespoons of flour and the baking powder until smooth. Do not over-aerate the mixture.
  8. Assemble the Bars: Slowly pour the lemon filling over the warm, par-baked shortbread base. Retrieve the reserved crumble mixture from the fridge and gently scatter it evenly over the top of the liquid filling.
  9. The Second Bake: Return the pan to the oven. Bake for an additional 18–20 minutes. The bars are done when the crumble topping is golden brown and the filling still has a very slight wobble in the absolute centre.
  10. Cool Completely: Remove the pan and allow the bars to cool completely on a wire rack at room temperature for at least 2 hours until fully set. Use the parchment paper overhang to lift the bars out of the pan. Dust liberally with icing sugar before slicing into squares.