This HAM AND CHEESE BREAKFAST CASSEROLE is our favorite make ahead breakfast for any special occasion. This breakfast casserole with ham, cheese, bread, eggs, herbs, and more is sure to please everyone and just so easy to make!
Spray an 8-inch baking dish (1½-2 qt) with non-stick cooking spray.
Spread the cubed bread in the bottom of the dish.
Heat oil and butter in a large skillet over medium-low heat. Add diced onion, salt, black pepper and sugar. Sauté until onions are lightly caramelized, approximately 10 minutes. Be careful not to burn the onion.
In a medium bowl, whisk together the eggs, half and half, dry mustard, nutmeg, thyme, salt and pepper.
Spread the ham over the bread cubes, then spread the onion mixture on top of the ham. Layer on the Gruyere or Swiss cheese then pour the egg mixture over the cheese.
Press down gently on the top to ensure all bread cubes get soaked with the egg mixture. Cover and refrigerate overnight.
Before baking, warm the casserole on the counter for 15 minutes and preheat the oven to 350 degrees F.
Bake, uncovered, 40-50 minutes or until center is set and edges are bubbly and top begins to brown. A knife inserted in the center should come out clean.
If casserole is browning too soon, loosely cover it with foil near the end of the cooking time.