Special equipment: One 10- by 3- by 3-inch metal terrine
Allow the cioccolato scuro gelato to "warm" up a bit at room temperature for about 15 minutes. You can use a kitchen mixer to soften your gelato, but make sure that you place the mixer bowl and paddle in the freezer for at least 15 minutes beforehand. Mix the gelato in a chilled bowl until soft but not melting.
Take your clean, dry terrine and rub a tiny bit of oil over the entire interior surface using a clean paper towel. Make sure you get into the corners.
Line the terrine using a large piece of plastic wrap, leaving at least 6 inches of wrap over the sides. Push into the corners and smooth the wrinkles using a clean dry paper towel. Place the terrine in the freezer for 15 minutes to chill.
Remove the chilled terrine and working quickly, spoon the cioccolato scuro gelato into the bottom, filling it by one-third. Push the gelato down firmly into the corners using a small offset spatula. Level the surface, and then freeze for 1 hour.
Repeat the process with the white chocolate gelato, freezing for 1 hour, and then repeat with the bacio gelato, freezing for 1 more hour, making sure each layer is firm before adding the next.
After leveling the top, pour the chopped caramelized hazelnuts onto the surface. Take the plastic edges and cover the surface, pressing the nuts into the gelato. Freeze overnight.
To serve, remove the terrine from the freezer and let stand for about 8 minutes. Using the plastic wrap, slowly lift the gelato out of the terrine. Unwrap the plastic and invert onto a serving tray. You can tip the terrine on its side to view the nuts.
Run your knife under very hot water, wipe dry and slice the terrine. Do this before each slice. Serve it in slices, sandwiched between rectangular homemade sugar cookies or simply with some warm chocolate sauce.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.