01 - Preheat oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
02 - Distribute English muffin pieces evenly across the bottom of the prepared dish. Scatter diced Canadian bacon over the muffins.
03 - Whisk together eggs, milk, 1/2 tsp salt, and black pepper in a large bowl until fully combined. Pour mixture evenly over the muffin and bacon layers.
04 - Cover the dish tightly with aluminum foil. Refrigerate for at least 1 hour, preferably overnight, to allow the bread to absorb the egg mixture.
05 - Remove casserole from refrigerator while oven preheats. Sprinkle paprika evenly over the top. Bake covered for 30 minutes, then remove foil and bake an additional 15-20 minutes until center is set and top is golden brown.
06 - Set up a double boiler with a heatproof bowl over gently simmering water. Whisk egg yolks, lemon juice, 1/4 tsp salt, and cayenne pepper for 2-3 minutes until slightly thickened. Slowly drizzle in warm melted butter while whisking constantly until sauce becomes thick and glossy.
07 - Let the baked casserole rest for 10 minutes before slicing. Cut into squares and serve warm, generously topped with freshly prepared hollandaise sauce.