White-Chocolate Semifreddo

1 . Stage

Fill a large bowl halfway with ice water. Combine egg yolks, sugar, and amaretto in a heatproof bowl set over a pan of simmering water. Whisk until mixture is pale and thickened, about 2 minutes. Strain through a fine sieve into a small bowl. Place bowl in ice water until mixture has cooled slightly. Press plastic wrap directly over the surface, and refrigerate for at least 30 minutes.

2 . Stage

Beat cream until stiff peaks form. Gently fold in the white chocolate, then the chilled yolk mixture.

3 . Stage

Spoon mixture into one 4-by-2-inch baking ring set on a parchment-lined baking sheet or two 6-ounce ramekins, filling them to the rim. Smooth surface. Cover, and freeze until set, about 2 hours (or up to overnight).

4 . Stage

Preheat oven to 350 degrees. Spread hazelnuts on a rimmed baking sheet, and toast until skins have split, 18 to 20 minutes. Let cool slightly, then rub with a damp towel to remove skins. Coarsely chop.

5 . Stage

If using a ring, run a knife around edge to loosen, and unmold. If using ramekins, do not unmold. Sprinkle with hazelnuts just before serving.