Line a deep casserole dish with a layer of bread slices spread with prepared mustard. Alternate bread layers with grated Crowley medium sharp cheese sliced thinly. Repeat until the bowl is full.
Beat several eggs (as many as your conscience will allow) with sufficient milk to flood the casserole and bake in a 350-degree oven until it balloons like a popover. When removed from the oven, the balloon will collapse and the dish is ready to serve.