Line bottom and sides of 8- or 9 x 3-inch springform pan with ladyfingers. Soften gelatine in lemon juice. In top of double boiler, with electric mixer, beat egg yolks well with ½ cup of sugar, and salt. Gradually beat in gelatine mixture. Cook over boiling water, stirring constantly, until mixture starts to thicken, about 10 minutes. Pour into large bowl; add lemon peel. Refrigerate until mixture begins to thicken, about 30 minutes, stirring occasionally (or chill over ice cubes in a larger bowl, stirring frequently, about 15 minutes). In heavy 2-to-3-quart saucepan, stir together egg whites and remaining ½ cup of sugar. Over very low heat, with electric mixer, beat egg whites until soft peaks form (or beat in bowl or double boiler over simmering water). Remove from heat and cool slightly. Fold beaten egg whites and whipped cream into lemon-gelatine mixture. Spoon into ladyfinger-lined pan. Chill for 3 hours or overnight. Carefully remove sides of springform pan. Garnish with lemon cartwheel slices and fresh mint leaves, if desired.
Source: Diana Baker Woodall