Grease a 9×13-inch baking dish with cooking spray or butter.

Preheat your oven to 375°F (190°C).

In a large mixing bowl, whisk together milk, eggs, sliced green onions, onion powder, and salt.

Layer half of the diced Canadian bacon in the baking dish, followed by all the diced English muffins, then add the remaining Canadian bacon.

Pour the egg mixture over the casserole, ensuring all layers are soaked.

Cover the casserole tightly and refrigerate for at least 8 hours.

Bake covered for 30 minutes, then uncover and bake for an additional 15 minutes.

In a saucepan, prepare Hollandaise sauce while the casserole is baking.

Slice the casserole into 10 portions and drizzle with Hollandaise sauce before serving.