I ate a lot of breakfast casseroles growing up. Anytime there was a crowd to be fed before noon, this baked dish of egg, sausage, cheese, and day-old bread would appear. And yet, as an adult, I’ve discovered that the classic breakfast casserole is a relative mystery to many of our friends.

This recipe is an updated version of the gooey cheddar and sausage casseroles of my youth, and it was inspired by a fancy ham and cheese sandwich. We used pancetta and Gruyere (although you could try an even more sophisticated cheese) with challah bread and caramelized onions for a touch of sweetness. Then we added nutmeg and thyme to brighten things up.

I’m afraid I’ll sound horribly hyperbolic if I talk about this recipe too long: It’s rich, eggy, and unbelievably, incredibly delicious. This is one to memorize, folks, and to pull out for in-laws and overnight guests. It may just be the very best brunch casserole I’ve ever made.

Why you’ll love it

Key ingredients in pancetta and Gruyere breakfast casserole

Make-ahead and storage tips

Pancetta and Gruyère Breakfast Casserole

Serves 6 to 8

Unsalted butter or cooking spray

4 cups (loosely packed) day-old challah or other egg-enriched bread (3/4-inch cubes)

2 tablespoons olive oil, divided

1 medium yellow onion, thinly sliced

3/4 teaspoon kosher salt, divided

1/4 teaspoon granulated sugar

8 ounces thickly sliced pancetta, diced

6 large eggs

1 1/2 cups whole milk

1/2 teaspoon dry mustard

1/4 teaspoon freshly grated nutmeg’

2 teaspoons fresh thyme leaves

1/4 teaspoon freshly ground black pepper

1 cup grated Gruyere cheese (about 4 ounces)

1. Grease an 8-inch square baking dish (or another 1 1/2-quart to 2-quart baking dish) with unsalted butter or cooking spray. Spread 4 cups challah bread cubes on the bottom of the baking dish.

2. Heat 1 tablespoon of the oil in a medium skillet over medium heat until shimmering. Add one thinly sliced medium yellow onion, 1/4 teaspoon of the kosher salt, and 1/4 teaspoon granulated sugar. Cook, stirring occasionally, until lightly caramelized (a medium golden-brown color), about 15 minutes.

3. Meanwhile, in another heavy skillet, heat the remaining 1 tablespoon oil over medium heat and saute 8 ounces diced pancetta until the fat is almost all rendered and it begins to get crisp, about 8 to 10 minutes. Transfer to a paper towel-lined plate to drain.

4. Whisk six large eggs, 1 1/2 cups whole milk, 1/2 teaspoon dry mustard, 1/4 teaspoon grated nutmeg, 2 teaspoons fresh thyme leaves, the remaining 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper together in a large bowl.

5. Spread the pancetta over the bread cubes, then layer the onions on top. Sprinkle 1 cup grated Gruyere cheese on next, and then pour the egg mixture over the entire thing.

6. Press down on the top gently, so that all of the bread cubes get soaked a bit with the egg mixture. Cover and refrigerate overnight.

7. Arrange a rack in the middle of the oven and heat to 350 F. Take the casserole out of the refrigerator so it can warm on the counter while the oven preheats.

8. Bake, uncovered, until the edges are bubbling and the top begins to brown, 35 to 50 minutes. The baking time will be greatly dependent on the depth of dish you use. Check the interior with a knife; if it comes out clean the bread custard is baked through. (Cover with aluminum foil near the end of cooking if the top is already browned.)

(Elizabeth Passarella is a contributor to TheKitchn.com, a nationally known blog for people who love food and home cooking. Submit any comments or questions to editorial@thekitchn.com.)

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