Lightly toast the coconut flakes in a pan, free of fat. Separate eggs. Beat the egg whites with the powdered sugar until the mixture has tripled. Stir in egg yolks, eggnog, coconut flakes and chopped walnuts. Finally fold in the very stiff whipped cream.
Rinse a metal box dish with cold water and pour the cream into the damp dish. Place in the freezer for at least 6 hours.
Before serving, briefly put the mold in hot water, turn it out and garnish with walnut halves.