Spray a 2 quart casserole dish or a 9x13-inch pan with cooking spray.
Place the English muffin pieces in the pan, then top with Canadian bacon pieces.
In a bowl, whisk the eggs together with the milk, onion powder, pepper and salt, then pour over the English muffins.
Lay the Swiss cheese strips over the top, then sprinkle with the mozzarella.
Cover the pan with plastic wrap and place in the refrigerator overnight.
Preheat the oven to 375° and place the pan in the oven. Bake for 35-40 minutes, until the eggs have cooked.
While the casserole is baking, make the hollandaise sauce.
When the casserole has finished baking, remove, cut slices and pour some hollandaise sauce over each serving.