Using a food processor, finely grind the sugar; set 3 tablespoons aside, leaving 1 tablespoon in the food processor. Add the nuts and pulse until finely chopped.
Using a mixer, beat the egg whites on medium speed until thick and foamy. Gradually add the reserved 3 tablespoons sugar, beating until the meringue is thick and glossy.
Line a baking sheet with parchment paper. Fold half of the nut mixture into the meringue and transfer to a 1/2-gallon plastic bag. Cut a 1/4-inch hole in a corner of the bag and pipe four 3-inch rounds onto the lined baking sheet, filling the center in a circular motion. Bake until crisp, about 30 minutes. Let cool completely.
In a medium bowl, combine the heavy cream and caramel sauce. Using a handheld mixer, whip until stiff peaks form.
Place 1 meringue round on a plate, top with a large dollop of caramel whipped cream, sprinkle with some of the nut mixture, then top with another meringue, more cream and another sprinkle of the nut mixture. Repeat to make a second meringue stack. Refrigerate for 15 minutes or up to 2 hours.