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
7 oz caramel candies, unwrapped
1/2 cup creamy peanut butter
1/3 cup heavy whipping cream plus 1/4 cup
1 cup semisweet chocolate chips
Preheat oven to 350 degrees F. Line a 9×13 pan with aluminum foil, leaving several inches hanging over the short ends of the pan. Grease the foil with butter or cooking spray. Be sure to grease the sides thoroughly, or the caramel layer in the middle will stick.
Combine the butter and chocolate in a heavy bottomed medium saucepan and set over low heat, stirring occasionally until melted and smooth. Transfer the chocolate mixture to a large bowl. Add the sugar, eggs, and vanilla mixing until thick and glossy. This will take 1 or 2 minutes of vigorous mixing with a wire whisk, or about a minute using mixer with paddle attachment set on medium high speed. Whisk or stir in flour and salt. Transfer half of the batter (about 2 1/2 cups) to the baking pan and spread evenly. Bake for 20 minutes. Let the brownies cool for about 20 minutes but keep the oven on.
Stir the caramels, peanut butter, and 1/3 cup cream in a heavy medium saucepan over low heat until melted and smooth. Immediately spread the caramel mixture over the brownies (if you let it sit, it will get hard and difficult to spread). Mix in remaining 1/4 cup heavy cream to the remaining batter to thin it out a little because it will stiffen as it sits. Pour the remaining brownie batter evenly over the caramel mixture and spread gently to cover. If it is still difficult to pour, gently dollop large spoonful onto the caramel and allow the caramel to heat the batter. As it heats, it will become easier to spread. Sprinkle the chocolate chips. Bake for 20 minutes. Cool the brownies completely in the pan.
Grab the foil edges and lift the brownies out of the pan and cut them into squares. Brownies will keep, tightly wrapped, for a week at room temperature.