This all-time favorite of Tante Marie’s can be made up to four hours before serving. If using blueberries, it is best to fold them in to the lemon mousse. If using cut fruit is best to put the berries in first and then cover with the mousse.
Wash the berries, being careful not to get them too wet. Divide these equally among eight wine glasses or glass bowls, leaving a few aside for garnishing.
In the top of a double boiler, combine the egg yolks, sugar, lemon juice, and zest. Whisk together over gently simmering water until the mixture becomes thickened, about 4 minutes. Remove from the heat and let cool at room temperature.
Place the heavy cream in another bowl and beat with a whisk or an electric beater, until it forms soft peaks. Fold three-quarters of the cream into the cooled lemon mixture. In a separate bowl, beat the egg whites until stiff but not dry and fold this into the lemon mixture. Pour this over the berries in each glass. Whip the remaining cream until stiff. Decorate each glass with the whipped cream, the reserved berries and mint leaves. Chill until ready to serve.