01 -
Preheat the oven to 350°F. Line a 9x13 inch pan with parchment paper, ensuring there is an overhang to lift the bars, and set aside.
02 -
Cream together the softened butter and granulated sugar in a stand mixer with the paddle attachment for about 3 minutes (or use a hand mixer). Add egg yolk and vanilla, then mix to combine. Add the cake flour and kosher salt and mix just until combined into a shaggy, crumbly dough. Press the dough evenly into the prepared pan and bake for 20-22 minutes or until edges are lightly golden. Let the crust cool.
03 -
In a medium-sized saucepan, combine butter, sweetened condensed milk, brown sugar, heavy cream, and light corn syrup. Whisk until combined. Heat the mixture to a boil, then reduce to a medium-low simmer. Cook while whisking frequently until the caramel reaches 225°F (about 25-30 minutes). Remove from heat, whisk in vanilla, and pour over the cooled shortbread crust. Chill for 1 1/2 to 2 hours until set.
04 -
Microwave the heavy cream for 45 seconds to 1 minute. Pour the warm cream over the semi-sweet chocolate and let sit for 1 minute. Whisk until smooth and glossy. Pour the ganache over the set caramel layer and refrigerate until firm, about 1-2 hours or overnight.
05 -
Sprinkle flaky sea salt over the set chocolate ganache. Cut into squares and serve at room temperature.