In a saucepan over low heat, or in a metal bowl set over a pan of simmering water, whisk together the egg yolks and sugar. Stir in the heavy cream. Cook and stir until the mixture is very thick: a few drops dribbled onto the surface should be visible. Remove from heat, and stir in the butter until completely incorporated. Place a sheet of plastic wrap directly on the surface, and refrigerate overnight.
Preheat the oven to 400 degrees F (200 degrees C). Grease a 9-inch springform pan.
In a glass or metal bowl, whip egg whites with an electric mixer until it is able to hold a firm peak. In a separate bowl, stir together the ground almonds, baking powder, and confectioners' sugar. Using a whisk or rubber spatula, fold 1/3 of the egg whites into the almond mixture to lighten; fold in the remaining egg whites until well blended. Pour the batter into the prepared pan.
Bake for 30 minutes in the preheated oven, until the top of the cake springs back when pressed lightly. Cool cake, then remove from the pan. Spread the glaze on top, and serve.
