Place half of the Canadian bacon in a greased 13x9-inch casserole dish. Evenly spread the English muffins pieces on top and then add remaining bacon.
In a large bowl, whisk eggs, milk, salt, pepper and onion powder; pour over top. Cover and refrigerate 8 hours (or overnight).
When ready to bake, heat oven to 375°F. Top casserole with paprika. Bake covered for 35 minutes. Remove cover and bake for an additional 15 minutes. Prepare the hollandaise sauce during the last 15 minutes of baking.
In a double broiler or metal bowl over simmering water (don’t let bowl touch water), whisk together egg yolks, heavy cream, and lemon juice. Continue whisking until sauce is thick enough to coat back of spoon. Reduce heat to low. Drizzle in melted butter, whisking constantly. Add salt and pepper to taste. Serve sauce immediately with casserole.
Remove casserole from oven. Cut into squares and serve with hollandaise drizzled over the top of the casserole.