Pistachio Semifreddo

Pulse 1 cup pistachios with 1/2 cup plus 2 tablespoons sugar in a food processor until very finely ground. Add remaining 1/2 cup pistachios and pulse until just coarsely ground. Beat egg whites in a bowl with an electric mixer at medium speed until they just hold soft peaks. Beat in remaining 1/4 cup plus 2 tablespoons sugar, a little at a time, then increase speed to high and beat until meringue just holds stiff, glossy peaks. Beat cream with almond extract in a wide bowl with mixer at high speed until it just holds soft peaks. Fold meringue into cream gently but thoroughly, then fold in nut mixture in same manner. Spoon into a 2-quart dish and freeze, covered, until firm enough to scoop, about 4 hours. Let soften slightly before serving.