A light and luscious lemon mousse is the base of this recipe. It's a good stand-alone dessert, but here we've piped it into fancy glasses and layered it with fresh berries for an elegant presentation. The parfaits can be assembled a day in advance of serving; keep them covered with plastic wrap in the refrigerator.
From Food to Live By: The Earthbound Farm Organic Cookbook by Myra Goodman
Melt the butter in a small pan over low heat.
Place the eggs in the bowl of an electric mixer and beat on medium speed for 1 minute. Gradually add the sugar. Increase the speed to high and beat until the mixture is pale in color and very fluffy, about 5 minutes.
With the mixer running at low speed, add the butter and lemon juice.
Transfer the mixture to a heavy-bottom saucepan. Place over medium-low heat and cook, stirring constantly with a wooden spoon until the custard thickens, 5 to 10 minutes. The trick is to heat the custard enough to thicken it without scrambling the eggs. Don't let the custard simmer, and keep stirring! When the custard thickly coats the back of the wooden spoon so that if you draw your finger across it, the mark holds, it's done. (An instant-read thermometer will register 138 degrees F.)
Transfer the custard to a clean bowl. Press plastic wrap or wax paper against the surface and refrigerate until thoroughly cold. The wrap will prevent a skin from forming on the custard's surface.
Beat the cream with the lemon zest and rum, if using, until it forms soft peaks.
Whisk about half of the cream into the chilled custard to lighten the mixture, then fold the remaining whipped cream into the custard. Transfer the mousse to a pastry bag.
Rinse the berries and dry them thoroughly. Place a few berries in the bottom of a martini or wine glass. Pipe a layer of mousse over the berries. Top with another layer of berries and cover with more mousse. Repeat, ending with mousse on top. Garnish each serving with a mint leaf.
Refrigerate, covered with plastic wrap, until serving time.