Whisk together 2 cups of milk and 8 large eggs in a large mixing bowl until fully combined and frothy, which takes about 2 minutes.

Stir in chopped green onions, onion powder, and salt into the egg mixture. Mix until well-distributed, breaking up large clumps of onion.

In a greased 9x13-inch casserole dish, layer the diced Canadian bacon and cut English muffins evenly across the bottom.

Pour the creamy egg mixture evenly over the layered Canadian bacon and English muffins. Use a spatula to gently press down on the layers.

Sprinkle paprika over the top of the casserole. Cover tightly and refrigerate overnight or for at least 8 hours.

Preheat your oven to 350°F (175°C). Remove the casserole from the refrigerator and place it in the oven. Bake for about 45 minutes or until golden brown and a knife inserted in the center comes out clean.

Prepare hollandaise sauce according to package instructions or make homemade sauce with egg yolks, butter, and lemon juice.

Once baked, remove the casserole from the oven, let cool for a few minutes, slice into squares, and serve warm with hollandaise sauce.