Preheat the oven to 350°F (175°C). Grease and line an 8x8-inch square baking pan with parchment paper leaving an overhang for easy removal. In a medium bowl combine 1.5 cups all-purpose flour, 1/4 cup granulated sugar and 1/4 tsp fine salt. Cut 1/2 cup (1 stick) cold unsalted butter into small cubes and use a pastry cutter or your fingers to work it into the flour mixture until it resembles coarse crumbs. Press the dough evenly into the bottom of the prepared pan, compacting firmly with the back of a measuring cup or your hands to form an even crust layer (about 1/4–1/3 inch thick). Bake for 15–18 minutes, or until the edges are just turning golden. Remove from oven and set aside while preparing the caramel.

Caramel filling

Cook the caramel

In a medium heavy-bottomed saucepan over medium heat melt 3/4 cup (1 1/2 sticks) unsalted butter. Add 1 cup packed light brown sugar and 2 tablespoons light corn syrup (if using). Stir to combine, then bring mixture to a gentle boil, stirring constantly so sugar fully dissolves. Once at a simmer, cook without stirring but gently swirling the pan for about 3–5 minutes until the mixture thickens and deepens slightly in color. Carefully whisk in 1/2 cup heavy cream (mixture will bubble vigorously), then reduce heat to low and cook another 1–2 minutes until the caramel is glossy and coats the back of a spoon. Remove from heat and whisk in 1/2 teaspoon fine salt and 1 teaspoon vanilla extract. Let the caramel cool for 4–6 minutes so it thickens slightly but is still pourable.

Assemble caramel over crust

Pour the warm caramel evenly over the pre-baked crust, spreading with a spatula into the corners. Tap the pan gently on the counter to release any air bubbles and to level the caramel layer. Allow the caramel to rest while you chop the Skor bars.

Crunch layer — chopped Skor pieces

Chop and distribute candy pieces

Coarsely chop 12 Skor bars (about 2 bars per 2-inch length, depending on size) into roughly 1/4–1/2-inch pieces. Scatter about two-thirds of the chopped Skor pieces evenly over the still-warm caramel, pressing down lightly so they adhere. Reserve the remaining chopped pieces for the top after the chocolate layer.

Chocolate topping

Make and pour ganache

Place 1.5 cups semisweet chocolate chips in a heatproof bowl. In a small saucepan heat 1/4 cup heavy cream over medium until it just begins to simmer; do not boil. Pour the hot cream over the chocolate chips and let sit 1 minute, then stir until smooth and glossy. If desired, stir in 1 tablespoon unsalted butter for extra shine. Let the ganache cool 1–2 minutes so it thickens slightly but is still pourable, then pour it over the caramel and Skor layer, spreading gently to coat evenly.

Finish & chill

Top and set

Immediately sprinkle the reserved chopped Skor pieces evenly on top of the warm chocolate so they adhere. Lightly sprinkle 1/4 teaspoon sea salt flakes across the top for contrast. Let the entire pan cool at room temperature for 30–45 minutes, then transfer to the refrigerator for at least 2 hours (preferably 3–4 hours) until fully set and easy to slice cleanly.

Slice and serve

Use the parchment overhang to lift the set slab from the pan. Place on a cutting board and, using a sharp knife warmed under hot water and wiped dry between cuts, slice into 16 squares. Serve chilled or at cool room temperature. Store leftovers in an airtight container in the refrigerator for up to 1 week.