Coffee-infused frozen cream dessert is Italy's answer to ice cream cake. This elegant mediterranean semifreddo is a family favorite for dinner parties.
Chill a metal loaf pan in the freezer for at least 1 hour to ensure the semifreddo sets quickly.
Whip the heavy cream in a mixing bowl with a hand mixer on medium-high until soft peaks form; refrigerate until needed.
Combine egg yolks, sugar, espresso, coffee liqueur, and salt in a heatproof bowl. Set over a pot of gently simmering water (double boiler), whisking constantly for 4–6 minutes until mixture is thick, pale, and reaches 160°F, then remove from heat.
Whisk in mascarpone and vanilla extract until smooth. Let cool to room temperature, stirring occasionally to prevent skin from forming.
Beat egg whites to stiff peaks, then gently fold into the coffee-mascarpone mixture. Next, fold in the chilled whipped cream in two additions, maintaining as much air as possible.
Pour the mixture into the chilled pan, level with a spatula, and cover with plastic wrap. Freeze at least 3 hours, preferably overnight, until firm but sliceable.
Let the semifreddo sit at room temperature for 10 minutes before slicing for optimal texture. Serve immediately for best flavor and consistency.