Preheat your oven to 350°F (175°C). Grease your baking pan or line it with parchment paper for easy removal later.
In a double boiler or microwave-safe bowl, combine the unsweetened baking chocolate, 3 ounces of semi-sweet baking chocolate, and 10 tablespoons of unsalted butter. Heat gently until melted and smooth, stirring occasionally. Allow to cool slightly.
In a large mixing bowl, whisk together the granulated sugar and the remaining 3 tablespoons of unsalted butter until combined. Add the eggs, one at a time, mixing well after each addition. Stir in the vanilla extract.
Pour the melted chocolate mixture into the sugar and egg mixture. Stir until well combined. In a separate bowl, whisk together the cocoa powder, flour, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Gently fold in the chopped pecans and ¾ cup of caramel bits into the brownie batter. Be careful not to overmix.
Spread the batter evenly into the prepared baking pan. Bake in the preheated oven for about 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
While the brownies are still warm, in a small saucepan over low heat, combine the remaining ¼ cup of caramel bits and 2 teaspoons of milk. Stir until melted and smooth. Drizzle this gooey caramel over the brownies and use a knife to swirl it gently into the batter.
Top the brownies with pecan halves for a decorative touch. Allow the brownies to cool in the pan before slicing them into squares. Enjoy this delicious treat with friends and family!