This is a real treat for coffee and chocolate lovers. And it takes less than half an hour to make.
On the bottom of a 9-inch springform pan, center a piece of waxed paper slightly larger than the bottom (so it sticks out a bit). Assemble pan, keeping paper in place. Spray side of pan with nonstick spray; line with one long strip of waxed paper. Set aside.
In a large heatproof bowl set over (not in) a saucepan of simmering water, combine 3/4 cup sugar with egg yolks and espresso powder. Whisking constantly, cook mixture until pale, thickened, and nearly doubled in volume, about 5 minutes. Remove from heat; set aside to cool, about 10 minutes.
In a large bowl, using an electric mixer, beat cream with remaining 1/4 cup sugar until stiff peaks form. Whisk 1/3 whipped cream into cooled egg-yolk mixture; with a rubber spatula, fold in remaining whipped cream. Transfer mixture to prepared springform pan. Freeze until firm, at least 3 hours and up to 1 week.
Using a thin metal spatula, loosen semifreddo from paper, and carefully slide from pan to a chilled serving platter. Return to freezer until ready to serve. Just before serving, garnish with chocolate shavings and espresso beans.
You'll need a 9-inch springform pan (but no ice cream machine!). It can be made and frozen up to one week ahead.