-
1
Spray a 9x5x3 inch metal loaf pan with nonstick cooking spray.
-
2
Line the pan with plastic wrap, allowing the excess to hang over the ends and sides.
-
3
Whisk 1/2 cup of the sugar, the egg yolks, lemon juice, lime juice, limoncello, and salt in a large metal bowl to blend. Stir in the zests.
-
4
Set the bowl over a saucepan of simmering water, making sure the bowl doesn't touch the water.
-
5
Whisk the egg mixture until it is thick and creamy, and a thermometer inserted into the mixture registers 160*F, about 5 minutes.
-
6
Set the bowl of custard into another bowl of ice water to cool completely.
-
7
Using an electric mixer, beat the cream and the remaining 1/4 cup sugar in another large bowl until firm peaks form.
-
8
Using a large rubber spatula, gently fold the whipped cream mixture into the custard.
-
9
Spoon the mixture into the prepared loaf pan.
-
10
Fold the overhanging plastic wrap over the custard and freeze until frozen, at least 8 hours or up to 3 days.
-
11
Unfold the plastic wrap.
-
12
Invert the semifreddo onto a platter and peel of the plastic wrap.
-
13
Cut the semifreddo into 1-inch slices, sprinkle with cookie crumbs and serve.
