- 2½ cups ripe blackberries
- One ½-pint ripe raspberries
- 1 cup sugar
- ¼ cup water
- Pinch of salt
- 3 large egg whites
- 1 cup heavy (whipping) cream
- Ripe berries, for serving (optional)
- STEP 1: Line a 9-by-5-inch loaf pan with 2 sheets of plastic wrap, leaving an overhang on all sides to make unmolding easy.
- STEP 2: Pulse the blackberries and raspberries in a food processor just until broken up. Pour the berries through a coarse strainer set over a bowl, pressing hard on the solids to extract as much liquid as possible.
- STEP 3: Bring the sugar, water, and salt to a boil in a small saucepan over high heat, stirring until the sugar is dissolved. Boil for 2 minutes. Remove from the heat.
- STEP 4: Beat the egg whites with an electric mixer on medium speed in a large bowl until foamy. Increase the speed to medium-high and, with the mixer running, slowly pour the hot sugar syrup into the egg whites, being careful to avoid the beaters. Continue beating for 8 to 10 minutes, until the egg whites are cooled to room temperature.
- STEP 5: Beat the cream on medium-high speed in a large deep bowl until it forms stiff peaks when the beaters are lifted. With a whisk or a rubber spatula, fold the berry puree into the egg white mixture until almost blended, then fold in the whipped cream.
- STEP 6: Spoon into the loaf pan and spread into the corners with a rubber spatula. Cover with the plastic and freeze for at least 6 hours, or overnight.
- STEP 7: About 15 minutes before serving, remove the semifreddo from the freezer. Fold back the plastic wrap, invert the semifreddo onto a serving platter, and peel off the plastic. Let stand for 10 minutes to soften slightly. Serve, cut into thick slices, with the berries, if using.