Grease 9×13-inch glass baking dish with Kerrygold butter. Place bread in prepared dish. Top with sausage and cheese. Beat together eggs and next three ingredients. Season with pepper. Pour over sausage mixture. (Can be prepared 1 day ahead. Chill.) Preheat oven to 350°F. Bake casserole until puffed and center is set, about 50 minutes. Cut into squares.