8 T unsalted butter
1 1/2 cups sugar
Grated zest of 1 large lemon
Juice of 3 large lemons
1/4 tsp salt
3 large eggs plus 3 large egg yolks
1 cup heavy cream
Melt the butter in the top part of a double boiler over barely simmering water (the water should not touch the bottom of the insert). Whisk in the sugar, lemon zest and juice, and salt. Beat the eggs and yolks together with a whisk in a medium bowl, and add to the ingredients in the double boiler. Cook over the barely simmering water, whisking constantly, until the mixture is smooth and glossy, and very thick, 3 to 5 minutes. *I have made this several times and it’s taken about 45 minutes to come to the consistency described. Do not let the curd boil, or it will curdle. Strain into a bowl, press a piece of plastic wrap directly on the curd to keep a skin from forming, and let cool in the refrigerator.
When the lemon curd is cold, whip the cream in a chilled bowl with a whisk or electric mixer until it holds soft peaks. Fold the whipped cream into the lemon curd with a rubber spatula until thoroughly combined. Pour into a metal serving bowl, cover with plastic wrap, and freeze until firm and set, about 6 hours. Serve from the bowl.