Method
 

1. Whisk the butter and egg yolks together in a Bain-Marie (bowl over a saucepan of water).

2. Add the flour and sugar and blend well.

3. Gradually stir in the milk.

4. Cook over medium heat, stirring constantly, until the mixture thickens slightly, about 10 minutes.
   Cool.

5. Add the vanilla to the cream and whip until stiff.

6. Beat the egg whites until stiff.

7. Fold the whipped cream and beaten egg whites into the custard.

8. Refrigerate until needed.

9. Sprinkle with freshly grated nutmeg before serving.