Ingredients:

  • 1 lb unsalted butter, softened
  • 1 cup granulated white sugar
  • 1.5 cups powdered sugar
  • 2 tbsp pure vanilla extract
  • 4 cups all-purpose flour, leveled
  • 1 cup salted butter, cubed
  • 1 cup light brown sugar, packed
  • 28 oz sweetened condensed milk (two 14 oz cans)
  • 2 tbsp light corn syrup
  • 1 tsp fine sea salt
  • 1 tbsp flaked sea salt

Instructions:

  1. Preheat your oven to 325°F (165°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
  2. In a large mixing bowl or stand mixer, cream the 1 lb of softened unsalted butter with the granulated sugar and powdered sugar until light and pale. Stir in the vanilla extract.
  3. Gradually add the all-purpose flour on low speed until a soft dough forms. Do not overmix.
  4. Measure out and set aside 2 cups of the dough to be used for the crumble topping. Press the remaining dough firmly and evenly into the bottom of the prepared 9x13 pan.
  5. Bake the crust for 18–20 minutes until the edges are just barely starting to turn a light mahogany color. Remove from the oven and let cool slightly while preparing the filling.
  6. In a medium heavy-bottomed saucepan, combine the 1 cup cubed salted butter, light brown sugar, sweetened condensed milk, and light corn syrup. Whisk over medium-low heat until the butter is melted and the mixture is fully emulsified and smooth.
  7. Stir the fine sea salt into the caramel mixture. Pour the hot caramel evenly over the pre-baked shortbread base.
  8. Crumble the reserved 2 cups of dough over the top of the caramel layer. Sprinkle the flaked sea salt over the top.
  9. Return the pan to the oven and bake for an additional 25–30 minutes until the filling is bubbly and the crumble topping is golden brown.
  10. Remove from the oven and allow to cool completely at room temperature. Refrigerate for at least 3 hours (essential for clean slicing) before cutting into 24 squares.