½ cup pecans
12 ounces chocolate pound cake, cut lengthwise into ½-inch-thick slices
4 ounces bittersweet chocolate, chopped
½ cup heavy cream, at room temperature
1 pint firm coffee chocolate chip ice cream
1 pint firm chocolate ice cream
1 pint firm dulce de leche ice cream
¼ cup water
1½ cups sugar
6 large egg whites, at room temperature
Pinch of salt
Pinch of cream of tartar
Preheat the oven to 350°. Spread the pecans in a pie plate and toast for 8 minutes, until fragrant. Let cool completely, then transfer to a food processor. Crumble one-third of the pound cake into the food processor and pulse with the pecans until coarsely chopped.
In a microwave-safe bowl, heat the chocolate at high power in 30-second bursts until it is nearly melted. Whisk until smooth, then whisk in the cream. Stir the pecan-cake crumbs into the ganache.
Line a 12-cup, flat-bottomed vessel with strips of parchment paper, making sure the paper extends by 4 inches on all sides. Arrange half of the cake slices neatly on the bottom of the vessel (you may have to cut them to fit). Remove the coffee chip ice cream from the carton and carefully slice it into slabs. Fit the slabs over the cake and press to an even layer. Spread with half of the nutty ganache and freeze until firm, about 1 hour.
Repeat the layering with the chocolate ice cream, the remaining nutty ganache and the dulce de leche ice cream. Top with the remaining cake slices. Fold the paper over the cake and freeze overnight or until very firm.
Remove the cake from the vessel and place it on a cake plate. Remove the paper. Return the cake to the freezer.
In a medium saucepan, bring the water to a boil with the sugar, stirring until dissolved. Brush down any sugar crystals from the side of the pan with a wet pastry brush. Boil for 2 minutes. Meanwhile, in the bowl of a standing electric mixer fitted with the whisk, beat the egg whites with the salt and cream of tartar until soft peaks form. With the machine at medium speed, carefully beat in the hot sugar syrup until incorporated. Increase the speed to high and beat until the meringue is stiff and glossy and no longer hot, 5 minutes.
Using a spatula, spread half of the meringue all over the cake. Fill a pastry bag fitted with a plain tip with the remaining meringue and pipe peaks on top. Using a pastry torch, toast the meringue until browned in spots. Return the cake to the freezer for 15 minutes. Cut the cake with a slightly moistened knife and serve right away.