makes approximately 24 squares
3 large eggs2 large egg yolks
1/2 vanilla bean, split lengthwise and scraped, seeds reserved
1 cup superfine sugar
3(5.6-ounce) packages fresh blackberries, divided
1 teaspoon fresh lemon zest
1 tablespoon fresh lemon juice
2 cups heavy cream
Garnish: fresh blackberries and fresh mint
1. In a large heatproof bowl set over a saucepan of boiling water, combine the eggs, egg yolks, vanilla-bean seeds, and sugar. Cook, whisking constantly, until frothy, 5 to 6 minutes. Remove from heat. Using an electric mixer at medium-high speed, beat until soft peaks form. Set aside.2. In a medium bowl, combine 2 packages blackberries, lemon zest, and lemon juice. With a fork, lightly mash the berries. Fold the berry mixture into the egg mixture. Set aside.
3. In a large bowl and using an electric mixer at high speed, whip the cream until soft peaks form. Gently fold the whipped cream into the egg-berry mixture. Set aside.
4. Line a9-x-9-x-2-inch baking dish with plastic wrap, allowing wrap to hang over by 2 inches on each end. Scatter remaining blackberries in prepared dish. Pour whipped-cream mixture over blackberries. Cover with foil, and freeze overnight.
5. Using plastic wrap as handles, lift frozen semifreddo from pan. Remove plastic wrap. Cut semifreddo into 24 (1 1/2-inch) squares. Garnish with fresh blackberries and fresh mint, if desired.