Preparation

Make the brownies

• Position a rack in the center of the oven and heat the oven to 350°F. Butter the bottom and sides of a 9×13-inch baking pan. Put the butter and chocolate in a medium heavy-duty saucepan over low heat and stir constantly until melted and smooth. Remove from the heat and set aside.

  In a medium bowl, whisk the eggs until well blended. Gradually whisk in the sugar and then whisk vigorously until well blended. Whisk in the melted chocolate mixture, vanilla extract, and salt. Whisk in the flour and cocoa powder until blended. Stir in the pecans and then scrape the batter into the prepared pan, smoothing it into an even layer with a spatula.

  Bake until a toothpick inserted in the center of the brownies comes out with a few moist crumbs clinging to it, 20 to 22 minutes. Transfer the pan to a wire rack and, if necessary, gently press down any puffed areas with a spatula to make the top level. Let cool about 5 minutes.

Make the topping

• While the brownies are baking, make the Basic Caramel according to the directions. Remove the pan from the heat and carefully add the cream—the mixture will bubble up furiously. Once the bubbling has subsided, add the butter and gently whisk until completely melted. Whisk in the vanilla extract and salt. Pour the caramel topping over the brownies, using a spatula to spread it evenly over the entire top. Let the brownies cool on the rack for 45 minutes and then refrigerate until the caramel topping is set, at least 1 hour.

Garnish the brownies

• Combine the chocolate and heavy cream in a small saucepan over low heat and stir constantly until melted and smooth. Pour the chocolate into a small piping bag fitted with a 1/8-inch plain tip. (Or put it in a small zip-top bag and seal the bag. Using scissors, snip off a corner of the bag to make a small hole.) Drizzle the chocolate over the brownies in a zigzag pattern. Sprinkle the chopped pecans over the top. Refrigerate until the chocolate is set, about 30 minutes.

  Cut the brownies into 36 rectangles. Serve chilled or at room temperature.

Make Ahead Tips

Well-covered brownies will keep at room temperature for up to 2 days and in the refrigerator for up to 5 days.