Biscuit tortoni is like a frozen mousse, but richer and more interesting in texture. You can add rum instead of vanilla, if you prefer. This is my favorite frozen dessert.
Combine the sugar and water in a saucepan and cook, without stirring, until the mixture reads 230° on a candy thermometer.
In a very large bowl, beat the egg whites until stiff. Slowly stir the sugar syrup into the egg whites and mix well. In another bowl, beat the egg yolks until thick and pale, and fold into egg white mixture, stirring well.
Pulverize the macaroons in a blender, or crumble them into fine crumbs between your fingers. Keep out
Whip the cream until stiff. Fold carefully and thoroughly into the mixture [by this time, the amounts will be enormous, so I find it best to use a big preserving kettle to mix the cream and egg mixture together], then sprinkle the reserved macaroon crumbs on top, and freeze in individual cups. [I use clear plastic, disposable, 5-ounce cups for a crowd.]
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