This is our favorite lemon mousse. This recipe is from Luscious Lemon Desserts which is an excellent cookbook. Serve the mousse with summer berries that are available now (strawberries, blueberries, blackberries etc.)
2 Tablespoons water
1 teaspoon unflavored gelatin
½ cup (1 stick) unsalted butter
¾ cup sugar
3 Tablespoons finely grated lemon zest
½ cup fresh lemon juice
Pinch of salt
6 large egg yolks
¾ cup whipping cream
Pour water into a small bowl and sprinkle the gelatin over the water and let stand about 10 minutes, or until softened. Place the bowl in a larger bowl of hot water, and stir until the gelatin has dissolved.
Meanwhile, melt the butter in a large heavy saucepan over medium-low heat. Remove the pan from the heat and whisk in the sugar, zest, lemon juice, and salt. Whisk in the yolks until smooth. Cook the mixture, stirring constantly, until it thickens and leaves a path on the back of a wood spoon when you draw your finger across. Do not allow the mixture to boil.
Remove the pan from the heat, stir in the gelatin mixture and immediately pour through a strainer into a bowl. Let cool to room temperature, whisking occasionally.
Beat the cream with an electric mixture on high speed in a large bowl until the cream forms stiff peaks. Do not over beat. Add the cream to the lemon mixture in 3 batches, gently folding it in with a whisk or rubber spatula until just blended.
Divide the mousse evenly between 4 stemmed glasses or container of choice. Refrigerate, loosely covered, for at least 2 hours or up to 2 days.