Preheat the oven to 375 degrees F (190 degrees C).
Beat eggs and milk together in a medium bowl.
Stir in flour.
Divide butter evenly into the cups of a 12-cup muffin tin, about 1/2 teaspoon per cup.
Place the muffin tin in the preheated oven until butter has melted and is sizzling hot, 2 to 3 minutes. Remove from oven, and distribute batter evenly among each cup.
Return to the oven and bake for 5 minutes. Reduce the heat to 350 degrees F (175 degrees C) and bake until puffed and golden, without peeking, about 25 minutes more.