Preheat oven to 350°F and line a second 8×8 baking pan (see note) with parchment paper. Set aside.
Melt the chocolate and butter in a saucepan over medium low heat until pieces are melted.
6 ounces unsweetened baking chocolate, 1 cup salted butter
Meanwhile, in the bowl of a stand mixer, beat the eggs on medium speed until light yellow (~ 5 minutes).
4 large eggs
Add sugar and blend on low until combined.
2 cups granulated sugar
Add vanilla and melted chocolate to the egg sugar mixture then add flour and beat until smooth.
1 tablespoon vanilla extract, ¾ cup all-purpose flour
Stir in caramel chips.
Pour batter into prepared pan.
Remove caramel from the freezer and lift parchment out of the pan.
Place on a cutting board and, using a sharp knife, cut caramel into squares.
Place caramel squares on top of brownie batter, spreading evenly over surface. (You will not use all of them).
Bake for about 45-55 minutes (toothpick inserted into center should come out clean when done – do not overbake).
Cool to room temperature then cover and refrigerate for at least one hour.
Spread top with the remaining salted caramel (warmed so it'll spread evenly), sprinkle with flaky sea salt, and cut into 16 squares
flaky sea salt