Step 1

Grease a 9x13 inch baking dish with butter or non-stick spray, set aside.

Step 2

Cook the sausage in a large skillet over medium-high heat until cooked through and no longer pink, drain and set aside.

Step 3

To the same skillet add the butter. Once the butter is melted, add in the diced onion, spinach, and sun dried tomatoes.

Step 4

Season with a pinch of salt and pepper and cook, stirring constantly for 5 minutes until spinach is wilted and onions are soft.

Step 5

Meanwhile, in a large bowl whisk together the eggs, milk, cream, mustard, garlic salt and pepper, and cayenne if using.

Step 6

Roughly tear the croissants into the bowl of egg mixture, along with half of the cheese, and stir well to combine.

Step 7

Pour the mixture into the prepared baking dish.

Step 8

Sprinkle the cooked sausage, and the spinach mixture, and remaining cheese over the casserole.

Step 9

Cover the dish with foil and refrigerate for at least 2 and up to 12 hours if possible.

Step 10

Preheat oven to 350 degrees. Remove the foil from the dish and bake for 30 minutes until cooked through.

Step 11

Serve immediately. Refrigerate leftovers for up to 3 days.