Layered Brownies with White-Chocolate Caramel and Cocoa Nib Gelato

Ingredients:
1/2 cup sugar
1/4 cup water
1 cup pecan halves, toasted
1/2 cup (1 stick) unsalted butter
2 ounces bittersweet chocolate (54% to 60% cacao), chopped
1/4 cup plus 1 teaspoon natural unsweetened cocoa powder
2 1/2 tablespoons all purpose flour
1/8 teaspoon salt
1/2 cup plus 1 tablespoon sugar
2 large eggs
1/2 teaspoon vanilla extract
3 tablespoons water, divided
3/4 teaspoon unflavored gelatin
4 1/2 tablespoons sugar
Pinch of salt
6 tablespoons heavy whipping cream
4 ounces high-quality white chocolate (such as Lindt or Perugina), finely chopped
1 1/2 tablespoons unsalted butter, diced, room temperature
2/3 cup heavy whipping cream
6 ounces bittersweet chocolate (54% to 60% cacao), chopped
Cacao Nib Gelato
8x8x2-inch metal baking pan

Instructions:
Lightly butter baking sheet. Stir sugar and 1/4 cup water in large nonstick skillet over medium heat until sugar dissolves. Increase heat and boil until sugar syrup is light golden, occasionally brushing down sides of skillet with wet pastry brush, about 8 minutes. Add pecans and stir until syrup coats pecans, about 1 minute. Immediately pour pecans out onto prepared baking sheet; spread in single layer with heatproof spatula. Cool completely. Coarsely chop nuts. DO AHEAD: Can be made 2 days ahead. Store airtight at room temperature.
Preheat oven to 350°F. Line 8x8x2-inch metal baking pan with foil. Butter foil. Combine 1/2 cup butter and bittersweet chocolate in heavy medium saucepan. Stir over medium-low heat until melted and smooth. Remove from heat; cool slightly. Whisk cocoa powder, flour, and salt in small bowl. Whisk sugar, eggs, and vanilla in medium bowl to blend. Pour butter mixture into sugar mixture; whisk until blended. Add cocoa mixture; whisk until blended. Transfer brownie batter to prepared baking pan; smooth top (layer will be thin).
Bake brownie until tester inserted into center comes out with moist crumbs attached, 18 to 20 minutes. Allow brownie to cool slightly, then gently press down on edges to form flat, even layer. Cool completely in pan on rack.
Spoon 1 tablespoon water into small bowl; sprinkle gelatin over and stir to blend. Let stand until gelatin softens, about 15 minutes.
Meanwhile, combine remaining 2 tablespoons water, sugar, and pinch of salt in heavy small saucepan. Stir over medium heat until sugar dissolves. Increase heat and boil until syrup is deep amber, occasionally swirling pan and brushing down sides with wet pastry brush, about 8 minutes. Slowly add cream (mixture will bubble vigorously). Reduce heat to low. Stir to dissolve any caramel bits. Remove from heat; let cool 5 minutes. Add gelatin mixture; stir until gelatin dissolves. Add white chocolate; whisk until melted and smooth. Whisk in butter. Pour caramel atop cooled brownie; spread evenly to cover completely. Chill uncovered until caramel firms slightly, at least 8 hours or overnight.
Bring cream to simmer in small saucepan. Remove from heat. Add chocolate; whisk until melted and smooth. Cool until mixture is slightly thickened but still pourable, about 15 minutes. Pour ganache atop caramel on brownie; spread just to edges. Sprinkle chopped candied pecans evenly over. Chill uncovered until ganache is firm enough to cut, about 4 hours. DO AHEAD: Can be made 2 days ahead. Cover and keep chilled.
Using foil as aid, lift brownie out of pan; place on work surface. Fold foil sides down. Using sharp knife, trim off about 1/4 inch of brownie on all sides. Cut brownie into eight 3 1/2-inch-long, 13/4-inch-wide bars. Place 1 brownie bar and scoop of Cacao Nib Gelato on each of 8 plates and serve.