1. Preheat oven to 375 degrees Fahrenheit.
2. Grease a 9×13 baking dish with butter.
3. Lay out English muffin halves on a flat surface. Top each one with a Canadian bacon slice, a heaping tablespoon of spinach and a slice of Swiss cheese between each English muffin. Carefully arrange the muffin stacks in the baking dish, slightly overlapping each other. Set aside.
4. In a separate bowl whisk together eggs, milk, yogurt, garlic powder, onion powder, paprika and nutmeg.
5. Pour the egg mixture over the top of the English muffins; press down on the English muffins so they are nearly submerged in the egg mixture. It's OK if the edges stick out from the egg mixture slightly. Cover the casserole dish and refrigerate overnight, or for at least 4 hours.
6. Bake, covered, for 30 minutes.
7. Remove cover and continue to bake for 25 to 30 more minutes, or until casserole is set and top of the muffins are golden brown.
8. Remove from oven.
9. Let stand for 10 minutes.
10. Serve with Hollandaise sauce.
Hollandaise Sauce Instructions:
1. Melt the butter in a microwave (make sure it’s covered as it will splatter) for about 1 minute, until it’s hot. Alternatively, you could heat it on the stove.
2. Add the egg yolks, lemon juice, Dijon, salt and cayenne pepper into a high-powered blender and blend for 5 seconds until combined.
3. With the blender running on medium-high, slowly stream in the hot butter into the mixture until it’s emulsified.
4. Pour the hollandaise sauce into a small bowl and serve while warm.