Grease a 9x13-inch baking dish with butter or cooking spray. Preheat your oven to 375°F.

Cut English muffins into quarters and toast until lightly crisp, about 5–7 minutes.

Layer half of the toasted muffin pieces in the dish, then half of the Canadian bacon, followed by the remaining muffin pieces and bacon.

In a large bowl, whisk together eggs, whole milk, heavy cream, Dijon mustard, onion powder, garlic powder, salt, and black pepper until smooth.

Pour the egg mixture over the layered muffins and bacon, pressing down gently to absorb.

Cover tightly with plastic wrap or foil and refrigerate for at least 4 hours or overnight.

Remove from the fridge and let sit at room temperature for about 20 minutes. Preheat the oven to 375°F.

Bake uncovered for 40–45 minutes until the top is golden brown and the center is set.

For the sauce, whisk egg yolks and lemon juice, then gradually whisk in melted butter until creamy. Add cayenne pepper and salt to taste.

Allow casserole to rest for 5–10 minutes before slicing. Serve warm with hollandaise sauce and garnish with chives or parsley.