Part 1: Prepare the Casserole Base (Can be done the night before)

1. Grease the Baking Dish: Generously butter a 9×13 inch baking dish or casserole dish. Ensure corners and sides are well-coated to prevent sticking.
2. Toast the English Muffins (Optional but Recommended): While not strictly necessary, lightly toasting the English muffin cubes helps them absorb the custard without becoming overly soggy. You can do this in a couple of ways:

   • Oven Method: Spread the cubed muffins on a large baking sheet. Bake in a preheated 350°F (175°C) oven for 8-10 minutes, or until lightly dried and slightly golden. Let cool.
   • Skillet Method: Melt 1 tablespoon of butter in a large skillet over medium heat. Add half the muffin cubes and toast, stirring occasionally, for 5-7 minutes until lightly golden and crisp. Remove and repeat with the remaining cubes (adding more butter if needed). Let cool.

3. Cook the Canadian Bacon: In the same skillet (no need to wipe it out if you used it for muffins), melt the remaining 1 tablespoon of butter (if needed; the bacon might render enough fat) over medium heat. Add the diced Canadian bacon and cook, stirring occasionally, for 4-6 minutes until lightly browned and slightly crisped. Remove with a slotted spoon and set aside, leaving any rendered fat in the skillet if desired for extra flavor (or discard if preferred).
4. Assemble the Base Layer: Spread half of the toasted English muffin cubes evenly across the bottom of the prepared baking dish. Sprinkle half of the cooked Canadian bacon over the muffins. If using cheese, sprinkle half of the shredded cheese over this layer.
5. Assemble the Top Layer: Top with the remaining English muffin cubes, followed by the remaining Canadian bacon, and finally the remaining shredded cheese (if using). Ensure an even distribution.
6. Prepare the Egg Custard: In a large bowl, whisk together the 10 large eggs until the yolks and whites are well combined and slightly frothy. Whisk in the whole milk or half-and-half, Dijon mustard, salt, black pepper, and ½ teaspoon paprika until thoroughly incorporated. Ensure there are no large streaks of yolk remaining.
7. Pour the Custard: Slowly and evenly pour the egg custard mixture over the assembled layers in the baking dish. Gently press down on the top layer of muffins with a spatula to help them absorb the liquid.
8. Chill (Crucial Step): Cover the dish tightly with plastic wrap or aluminum foil. Refrigerate for at least 4 hours, or preferably overnight (up to 24 hours). This chilling time is essential for the muffins to fully absorb the custard, ensuring a cohesive and flavorful casserole rather than distinct wet and dry layers.

Part 2: Bake the Casserole

1. Preheat and Prepare: Remove the casserole dish from the refrigerator about 30-45 minutes before baking to allow it to come closer to room temperature (this promotes even cooking). Preheat your oven to 350°F (175°C). Remove the plastic wrap or foil.
2. Bake: Place the casserole dish on the center rack of the preheated oven. Bake uncovered for 45-60 minutes. The casserole is done when it is puffed, golden brown on top, and a knife inserted near the center comes out clean (or with moist crumbs, but no liquid egg). The internal temperature should reach at least 160°F (71°C). If the top starts browning too quickly before the center is cooked, you can loosely tent it with aluminum foil for the remaining baking time.
3. Rest: Once baked, remove the casserole from the oven and let it rest for 10-15 minutes before slicing and serving. This allows the custard to set further, making slicing cleaner and allowing the heat to distribute evenly.

Part 3: Prepare the Hollandaise Sauce (While Casserole Rests)

• Using a Packet Mix: Prepare the Hollandaise sauce according to the package directions, typically involving whisking the mix with milk or water and butter over heat until thickened. Keep warm.
• Making Quick Blender Hollandaise (Recommended):

  1. Combine Ingredients: Place the 4 egg yolks, 2 tablespoons of fresh lemon juice, ½ teaspoon Dijon mustard (if using), and ¼ teaspoon salt in a blender container.
  2. Heat Butter: Ensure your ½ cup (1 stick) of unsalted butter is fully melted and hot. It should be bubbling slightly but not browned. Heat is crucial for emulsifying the sauce.
  3. Blend Yolks: Blend the yolk mixture for 5-10 seconds until combined and slightly pale.
  4. Emulsify: With the blender running on low-medium speed, very slowly drizzle the hot melted butter through the feeder cap opening. This slow addition is key to creating a stable emulsion. Continue blending until all butter is incorporated and the sauce is thick, smooth, and creamy (usually takes 30-60 seconds).
  5. Adjust Consistency & Seasoning: If the sauce is too thick, blend in a teaspoon or two of hot water until it reaches desired consistency. Taste and adjust seasoning, adding more salt or a pinch of cayenne pepper if desired.
  6. Keep Warm: Transfer the sauce to a small bowl or measuring cup. If not using immediately, place the container in a larger bowl of warm (not hot) water to keep it from cooling and thickening too much. Whisk occasionally. Hollandaise is best served fresh.

Part 4: Serve

1. Slice: Cut the rested casserole into squares or rectangles.
2. Plate: Place a portion of the casserole onto each plate.
3. Sauce: Generously spoon the warm Hollandaise sauce over each serving.
4. Garnish: Sprinkle with chopped fresh chives, parsley, and/or an extra dash of paprika for color and freshness. Serve immediately.