Preheat oven to 400F
In a medium bowl, beat eggs with milk. Stir in flour. Set aside.
Divide butter evenly into the twelve cups of a muffin tin, about 1/2 teaspoon per cup. Place tin in oven to melt butter, 2 to 5 minutes. Remove tin from oven, and distribute batter evenly among buttery cups.
Bake in preheated oven 5 minutes. Reduce heat to 375F, and bake 25 minutes more or until puffed and golden.