1 cup (2 sticks) unsalted butter
12 oz. bittersweet chocolate, coarsely chopped
1 1/2 cups sugar
4 large eggs
1 tablespoon vanilla extract
1 1/4 cups all-purpose flour
1/2 teaspoon salt
1 cup semisweet chocolate chips
14 oz. caramel candies, unwrapped
1/3 cup heavy cream
Preheat oven to 350 F. Line a 13×9 baking pan with aluminum foil, leaving an overhang on opposite sides to lift the brownies out. Spray thoroughly with cooking spray.
Place the butter and bittersweet chocolate in a microwave safe bowl and heat in 30-second bursts at 50% power, stirring in between, until completely melted and smooth. Add the sugar, eggs, and vanilla to the bowl and whisk vigorously until the mixture is thick and glossy. Stir in the flour and salt with a rubber spatula, mixing just until combined.
Transfer half of the batter to the prepared baking pan and spread in an even layer. Bake for 20 minutes. Transfer the pan to a wire rack and let cool for 20 minutes. Maintain oven temperature.
Meanwhile, add the caramels and heavy cream to a medium saucepan and set over medium-low heat. Cook, stirring frequently, until completely melted and smooth. Immediately pour the caramel over the brownies and spread evenly. (If you finish melting the caramels before the brownies have cooled for 20 minutes, just set the pan over very low heat to keep warm. Otherwise, the caramel will harden and be difficult to spread.) Dollop the remaining brownie batter over the caramel layer and spread to cover. (My brownie batter was thick so I microwaved it for 1 minute to make it more fluid.) Sprinkle the chocolate chips over the top of the brownies.
Bake for 20 minutes. Transfer the pan to a wire rack and let the brownies cool completely in the pan. Run a thin knife along the sides of the pan to loosen any caramel that might be stuck, then use the foil to lift the brownies from the pan and cut into squares for serving.