Don’t be daunted by the long ingredient list and multiple steps in the recipe below. This is quite an easy semifreddo to put together and requires no special tools or ice cream machines. It looks striking, with two distinct layers, one intensely blueberry-colored and flavored, the other creamier and richer in dairy notes. It tastes like summer on a plate, and the surprise element is definitely the pistachios, which have a real affinity for blueberries. I used Sicilian pistachios from Bronte, which are deeply green and very aromatic; but any unsalted pistachios will do. Store any leftover pistachios (or all nuts for that matter) in the freezer to stave off rancidity; the high fat content of nuts makes them turn faster than you’d like.
For the cooked blueberries:
- 3 cups blueberries
- 1 cup sugar
- 1 teaspoon cornstarch, dissolved in tablespoon cool water
For the dark mousse:
- ½ cup shelled unsalted pistachios
- ½ cup sour cream
- ¼ pound cream cheese, softened
- ½ cup heavy cream, chilled
For the swirled mousse:
- 3 ounces sweetened condensed milk
- 2 ounces milk
- ¼ cup sugar
- 3 ounces cream cheese, softened
- 1/4 cup plain Greek yogurt
- ½ teaspoon vanilla extract
- 12 shelled unsalted pistachios, finely chopped
Make the cooked blueberries: In a 1-quart saucepan, combine the blueberries with the sugar and bring to a light boil over medium heat. Cook, stirring, until jammy, about 10 minutes. Return to a vigorous boil, stir in the cornstarch slurry while whisking, and cook 30 seconds, or until glossy and the juices are thick. Remove from the heat and cool to room temperature.
Make the dark mousse: Preheat the oven to 350 degrees. Spread the pistachios out on a tray and roast in the preheated oven 8 minutes, or until toasty. Cool and coarsely chop. Set aside.
Place the sour cream and cream cheese in a food processor and add ½ cup of the cooked blueberries. Puree until smooth and set aside. In a large bowl, beat the heavy cream to soft peaks. Fold in the blueberry-cream cheese mixture until blended, without deflating the cream. Stir in the chopped pistachios and 1 cup of the cooked blueberries.
Line a loaf pan or terrine mold with plastic wrap, allowing excess to hang over the sides. Spoon the dark mousse into the mold and freeze until firm, about 4 hours.
Meanwhile, make the swirled mousse: Combine the condensed milk, milk, and sugar in a saucepan over medium heat; cook 3 minutes, or until the sugar dissolves and the mixture bubbles. Place the cream cheese in a medium bowl; gradually add the hot milk mixture, whisking until smooth.
Stir in the yogurt and vanilla. Cool completely. Stir in the remaining cooked blueberries until the mixture looks swirly; don’t overmix, as you want to keep the mousse looking marbled. Pour over the frozen dark mousse in the mold and sprinkle with the finely chopped pistachios.
Freeze until firm, then wrap tightly in the plastic wrap and keep frozen until ready to serve (up to 1 week).