1 env. unflavored gelatin
1/4 c. cold water
3 egg yolks
1/2 c. plus 3 tbsp. sugar
1/4 c. fresh lemon juice
2 tsp. finely grated lemon peel
1 c. heavy cream
3 egg whites
1 lemon, cut lengthwise into halves and cut crosswise into paper-thin slices
(optional)
1/2 c. heavy cream (optional)
1 tsp. confectioners sugar (optional)

In a heatproof measuring cup or small bowl, sprinkle the gelatin over 1/4 cup of cold water. When the gelatin has softened for 2 or 3 minutes, set the cup in a small skillet of simmering water and stir until the gelatin dissolves completely. Remove the skillet form the heat, but leave the cup of gelatin in the skillet.

With a wire whisk or a rotary or electric beater, beat the egg yolks with 1/2 cup of the sugar until the yolks are pale yellow and thick enough to fall back in a ribbon when the beater is lifted from the bowl. Stir in the dissolved gelatin, the lemon juice and the lemon peel.

With the same whisk or beater, whip the cream in a large chilled bowl until it is firm enough to hold its shape softly. Then, with a rubber spatula, gently but thoroughly fold the cream into the egg and lemon mixture, using an over-under cutting motion rather than a stirring motion.

Wash and dry the whisk or beater; then, in a separate bowl, use it to beat the egg whites until they are frothy. Sprinkle in the remaining 3 tablespoons of sugar and continue beating until the egg whites are stiff enough to stand in unwavering peaks when the whisk is lifted from the bowl. Gently fold the egg whites into the lemon mixture and continue to fold until no trace of white can be seen in the mixture.

Spoon the lemon cream into 6 individual dessert dishes or into a large serving bowl. Cover it tightly and refrigerate it for at least 3 hours before serving. If you like, you may garnish the dessert with lemon slices and whipped cream. Whip the cream with a wire whisk or a rotary or electric beater until it holds its shape softly. Sprinkle it with confectioners sugar and beat until the cream if stiff enough to form firm, unwavering peaks. With a pastry bag fitted with a decorative tip, pipe rosettes or decorative swirls of whipped cream on top of the dessert.