01 - Preheat your oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Spread the English muffin pieces evenly in the prepared baking dish. Top with the diced Canadian bacon.
03 - In a large bowl, whisk together eggs, milk, 1/2 tsp salt, and black pepper until well combined. Pour this mixture evenly over the muffin and bacon layer.
04 - Cover the dish with foil and refrigerate for at least 1 hour, or overnight for best results. This allows the bread to absorb the egg mixture.
05 - Remove the casserole from the fridge while the oven preheats. Sprinkle paprika over the top. Bake, covered with foil, for 30 minutes.
06 - Remove the foil and continue baking for 15–20 minutes, until the center is set and the top is lightly golden.
07 - While the casserole bakes, set up a double boiler: place a heatproof bowl over a pot of gently simmering water. Whisk together egg yolks, lemon juice, 1/4 tsp salt, and cayenne for 2–3 minutes until slightly thickened. Slowly drizzle in the melted butter, whisking constantly, until the sauce is thick and glossy. Remove from heat.
08 - Let the casserole rest for 10 minutes before slicing. Serve slices topped generously with warm hollandaise sauce.