4 eggs, separated
1 1/2 c. granulated sugar
1 pkg. (or 3/4 tbsp.) unflavored gelatin
1/4 c. cold water
1 tsp. cornstarch
1/2 c. fresh lime (or lemon) juice
2 tbsp. finely grated lime zest (or lemon peel)
4 tbsp. rum (optional)
1 1/2 c. heavy cream
3 tbsp. confectioners' sugar
Seasonal berries or berry sauce (optional garnish)

With an electric mixer, beat egg yolks and sugar together until pale yellow. Soften gelatin in the cold water. Place in the top of a double boiler over hot water and stir until dissolved. In a bowl, combine cornstarch with 3 tablespoons lime juice, stirring until smooth. Add remaining lime juice, lime zest and gelatin. Stir together well. Add lime juice mixture to egg yolk mixture. Whisk into a custard. Place lime custard mixture in top of a double boiler and cook over hot water, stirring constantly, until custard thickens, about 20 minutes. Add 2 tablespoon rum and cook, stirring 1 minute longer. Do not boil. Chill, covered, in a large bowl until mixture just begins to set. Whip heavy cream, slowly adding remaining rum and confectioners' sugar, until stiff. Gently fold the cream and egg whites into chilled lime custard with a rubber spatula. Chill. Serve in a large bowl or in individual dessert goblets. Garnish with fresh berries or berry sauce.