Bring milk and butter to a boil. Remove from heat and stir in the flour, mixing until mixture is smooth. Cool.
When mixture is lukewarm, stir in six of the egg yolks, one by one, mixing well after each addition. Form walnut-sized pieces of the dough and place two inches apart on a greased and floured baking sheet. Brush each with beaten egg yolk.
Bake at 375°F. for 30 minutes, or until golden brown and dry in the centers.