Prep the pan: Heat the oven to 350°F (175°C).
Grease a 9x13-inch baking dish with 1 tablespoon butter.
Cook the meat (optional): If your Canadian bacon or ham is not pre-seared, warm a skillet with 1 tablespoon butter. Sauté the meat for 3–4 minutes to develop flavor. Set aside.
Make the egg mixture: In a large bowl, whisk together the 10 eggs, heavy cream, and almond milk until smooth.
Season with 1 teaspoon salt and 1/2 teaspoon black pepper.
Add mix-ins: Stir in the chopped Canadian bacon, shredded cheese, and most of the green onions (save some for topping).
Assemble: Pour the mixture into the prepared baking dish. Smooth the top and sprinkle with a pinch of smoked paprika if you like.
Bake: Place in the oven and bake for 30–40 minutes, until the center is set and the edges are lightly golden. A knife inserted near the center should come out mostly clean.
Rest: Let the casserole stand for 10 minutes before slicing.
This helps it set and makes cleaner pieces.
Make the hollandaise (blender method): Melt 8 tablespoons butter until hot and fully liquid. In a blender, add egg yolks, lemon juice, Dijon, a pinch of salt, and a few dashes of hot sauce. With the blender running on low, slowly stream in the hot butter until the sauce thickens and turns glossy.
If it’s too thick, blend in 1–2 teaspoons warm water.
Season and serve: Taste the hollandaise and adjust salt and lemon. Slice the casserole, spoon warm hollandaise over the top, and finish with chives or parsley and a little paprika.