Remove crusts from bread and spread with butter.
Place buttered side down, pressing firmly into muffin cups.
Bake in 325º F (160ºC) oven for 10 minutes.
Meanwhile, combine eggs and milk in a large liquid measuring cup. Set aside.
Sauté bacon and green onions until both are cooked; drain fat.
Divide evenly between 12 bread cups. Pour a bit of egg mixture over top, allowing it to be partially absorbed, then add more. Sprinkle with cheese.
Bake in 325ºF (160ºC) oven for 16 to 18 minutes or until golden and puffed. (If edges brown before eggs are set, cover with aluminum foil)