One 7-inch heart-shaped Pate Brisee tart shell, baked and cooled.
- 1 envelope unflavored gelatin
- 1 tablespoon cold water
- 1/2 cup freshly squeezed lemon juice
- 1 cup sugar
- 7 egg whites
- 1 cup heavy cream
- Grated rind of 1 lemon
- In a small heavy saucepan, soften the gelatin in the water. Add the lemon juice and sugar and stir over a very low flame just until the gelatins thoroughly dissolved. Do not let it boil or cook too long.
- Remove from the heat and let cool to a syrup like consistency over a bowl of ice water. This mixture must be completely cooled before being added to the egg whites.
- Beat the egg whites until very stiff. Still mixing, slowly add the gelatin mixture. Whip the cream until stiff and gently fold it in. Take care to thoroughly incorporate all ingredients without deflating the egg whites and cream. Finally, fold in the grated rind.
- Mound the mousse in the baked tart shell and chill for at least 4 hours.
Source: Martha Stewart Pies and Tarts