With an electric mixer, beat the 3/4 cup butter, brown sugar and egg yolk until creamy and smooth. Slowly beat in the flour until there is an even dough-like consistency.
Dump the dough in a greased 13x9 cake pan. Press the dough evenly across the bottom of the pan.
Bake in a 350F for 20 minutes. Cool on a wire rack.
In a sauce pan heat the 2 tbsp butter and condensed milk over medium heat. Once it come to a boil stir constantly, scraping the bottom of the pan for 5 minutes. The sauce will thicken and become smooth. Stir in the vanilla. Spread the filling over the crust.
Bake in a 350F oven for 12-15 minutes. The top layer will bubble and become golden brown. Watch that it does not get 'too' brown. Remove from oven and let cool on a wire rack.
While the crust and caramel is still hot, sprinkle the chocolate chips across the caramel. Wait a few minutes. The chocolate chips will have melted. Using a spatula, spread the chocolate evenly across the baked layers.
Sprinkle the Skor toffee bits across the melted chocolate.