Grease a 9 × 13-inch baking dish with butter or nonstick cooking spray.
Spread half of the chopped Canadian bacon evenly over the bottom of the baking dish.
6 ounces Canadian bacon
Split the English muffins with a fork (to avoid crumbling), toast each half, and spread with a little butter.
6 sourdough English muffins, 2 Tablespoons butter
Chop the toasted muffins into bite-sized pieces.
Add half of the muffin pieces over the bacon, then repeat with another layer of bacon and muffin pieces.
In a large bowl, whisk together eggs, heavy cream, milk, salt, pepper, smoked paprika, mustard powder, and tarragon until well combined.
8 large eggs, 1¼ cups heavy whipping cream, ¼ cup whole milk, 1 teaspoon kosher salt, ½ teaspoon black pepper, ½ teaspoon smoked paprika, ½ teaspoon dry mustard powder, ½ teaspoon dried tarragon
Pour the egg mixture evenly over the bacon and muffin layers.
Cover the dish tightly with foil and refrigerate overnight or for at least 4 hours to allow the muffins to absorb the egg mixture.
Preheat the oven to 375°F.
Place the casserole in the oven (still covered) and bake for 35 minutes.
Remove the foil and continue baking for another 10–15 minutes, until the center is puffed, set, and a knife inserted in the center comes out clean.
Prepare the Hollandaise sauce according to the package instructions in a small saucepan.
1.25 ounces Hollandaise sauce mix
Drizzle the sauce over the warm casserole before serving.
Garnish with fresh chopped chives if desired.
fresh chopped chives