This frozen layered terrine is an ideal dessert to make ahead and so easy to pull out, slice, and serve when an elegant finish is called for. Keep it in mind when the weather turns warm. Wrapped in plastic, it holds well for 2 weeks in the freezer. The lemon zest garnish must be made at least 1 day ahead.
At Bottega, we serve the semifreddo on top of a basic génoise sponge (as pictured), but it’s not necessary.–Frank Stitt
Remove the zest from the lemons with a zester, making sure not to remove any of the bitter white pith. Place the zest in a small bowl, cover with boiling water, and let stand for 30 minutes. Drain.
Bring the sugar and cold water to a boil in a small saucepan over medium-high heat, stirring to dissolve the sugar.
Add the drained zest, reduce the heat to medium-low, and cook for 10 minutes. Transfer the zest and syrup to a bowl, cover, and let stand overnight.
The next day, transfer the zest and syrup to an airtight container. (The zest can be stored in the refrigerator for up to 2 weeks.)
Prepare an ice bath and set aside.
Whisk together the lemon juice, sugar, eggs, egg yolks, and butter in a large heavy saucepan and cook over medium heat, whisking constantly (do not walk away), until it begins to boil and becomes thick and pudding-like, 10 to 15 minutes.
Strain the curd through a fine-mesh strainer into a bowl, and set the bowl in the ice bath. Stir the curd periodically until it is cool, then remove the bowl from the ice bath and place a sheet of plastic wrap directly on the surface of the lemon curd. Refrigerate for at least 1 hour. (The curd can be refrigerated for up to 3 days.)
Whip 1 1/2 cups of the chilled heavy cream in a large mixing bowl with a wire whisk or electric mixer until soft peaks form. Remove the chilled lemon curd from the refrigerator, and set aside 1/2 cup for the sauce. Gently fold the remaining lemon curd into the whipped cream until well combined to create a soft lemon mousse. Refrigerate the reserved lemon curd. (It can be refrigerated, tightly covered, for up to 1 week.)
Arrange eight 3-inch ring molds or 6-ounce ramekins on a parchment-lined baking sheet. Spoon the lemon mousse into the molds, filling each with about 3/4 cup. Cover and transfer to the freezer to firm up for at least 4 hours. (The mousse can be frozen for up to 1 week.)
Drain the candied lemon zest, reserving the syrup for the sauce, and set the zest aside on a plate or sheet of parchment.
Whisk 1/3 cup of the lemon syrup with the remaining 1/2 cup lemon curd and the lemon juice in a small bowl; set the sauce aside.
To serve, remove the ring molds or ramekins from the freezer and let them warm up for 4 to 5 minutes. (If using ramekins, you can dip each one briefly in hot water to release the semifreddo.)
Meanwhile, whisk the remaining 1 cup chilled cream in a medium bowl until soft peaks form. Unmold the mouse onto individual dessert plates. Spoon the lemon sauce around the mousse, top with the whipped cream, and finish with a garnish of candied lemon zest.