This Ham and Caramelized Onion Strata is a breakfast casserole you’ll want to bring to all your brunch parties this season! Trust me. It’s incredibly delicious and simple! Layers of crunchy bread, gooey cheese, sweet caramelized onions, salty ham, and a hint of whole grain mustard make this breakfast one you’ll crave again and again.Distribute bread on two baking sheets and toast in the oven for about 10 minutes, until golden brown and dried out on top. Set aside to cool.In a large nonstick skillet, melt butter over medium-high heat. Add the onions and cook for 7 to 10 minutes, stirring occasionally, until softened. Turn heat down to medium-low, stir in ¼ teaspoon of the salt, and cook for 7 to 10 more minutes, stirring occasionally, until well-browned. Add spinach and ¼ teaspoon of the salt; cook for 1 to 2 minutes, until wilted. Remove pan from the heat and let cool for at least 5 minutes. Stir in the ham.In a bowl, whisk together the eggs, Half & Half, mustard, pepper, cayenne (if using) and remaining ¼ teaspoon salt.

Place half of the bread in the bottom of a greased 9 x 13-inch baking dish. Layer half of the onion mixture, then 1 ½ cups of the cheese (reserve remaining ½ cup in the refrigerator until ready to bake). Top with remaining bread and onion mixture. Whisk egg mixture again to recombine, then pour evenly on top. Cover with plastic wrap, then place a small sheet pan or rectangular plate on top. Weigh the surface down with something heavy (like a few cans of food or a few large plastic bags filled with sugar). Refrigerate at least 8 hours, or up to 24 hours.Sprinkle the reserved ½ cup cheese on top, then bake for 30 to 40 minutes, until no liquid remains in the center and the top is golden brown and crisp. Let cool for 5 minutes, then serve with extra mustard.

Ham and Caramelized Onion Strata
Serves 6 to 8

1 pound Italian bread loaf, cut into 1-inch cubes
3 tablespoon unsalted butter
1 large yellow onion, halved and thinly sliced
3/4 teaspoon kosher salt, divided
6 ounces fresh baby spinach leaves, roughly chopped
12 ounces (about 2 cups) cubed, fully cooked ham
2 cups shredded Colby jack cheese, divided
6 eggs
1 ¾ cups Half & Half
2 teaspoons whole grain mustard, plus more for serving
¾ teaspoon black pepper
Pinch cayenne pepper, optional

Preheat oven to 400°F.

Distribute bread on two baking sheets and toast in the oven for about 10 minutes, until golden brown and dried out on top. Set aside to cool.

In a large nonstick skillet, melt butter over medium-high heat. Add the onions and cook for 7 to 10 minutes, stirring occasionally, until softened. Turn heat down to medium-low, stir in ¼ teaspoon of the salt, and cook for 7 to 10 more minutes, stirring occasionally, until well-browned. Add spinach and ¼ teaspoon of the salt; cook for 1 to 2 minutes, until wilted. Remove pan from the heat and let cool for at least 5 minutes. Stir in the ham.

In a bowl, whisk together the eggs, Half & Half, mustard, pepper, cayenne (if using) and remaining ¼ teaspoon salt.

Place half of the bread in the bottom of a greased 9 x 13-inch baking dish. Layer half of the onion mixture, then 1 ½ cups of the cheese (reserve remaining ½ cup in the refrigerator until ready to bake). Top with remaining bread and onion mixture. Whisk egg mixture again to recombine, then pour evenly on top. Cover with plastic wrap, then place a small sheet pan or rectangular plate on top. Weigh the surface down with something heavy (like a few cans of food or a few large plastic bags filled with sugar). Refrigerate at least 8 hours, or up to 24 hours.

Preheat oven to 350°F. Uncover the baking dish and discard plastic wrap. Sprinkle the reserved ½ cup cheese on top, then bake for 30 to 40 minutes, until no liquid remains in the center and the top is golden brown and crisp. Let cool for 5 minutes, then serve with extra mustard.