Step by step

Method

4 steps

1. 1

   Heat the oven to 375°F and grease a 9-by-13-inch baking dish. Brown 1 lb breakfast sausage with 1 small diced yellow onion in a skillet over medium heat, 8–10 minutes, until the sausage is cooked through and the onion is soft. Stir in 5 oz baby spinach until just wilted, 1–2 minutes. Drain any big puddle of fat.

2. 2

   Spread 8 cups cubed day-old bread in the dish in an even layer. Spoon the sausage-spinach mixture over the bread, then scatter 1 cup shredded cheddar and ½ cup shredded Monterey Jack on top.

3. 3

   Whisk 10 large eggs with 2 cups whole milk, 1 teaspoon kosher salt, and ½ teaspoon black pepper until no streaks of white remain. Pour evenly over the casserole, pressing the bread down gently so it soaks. Rest 10 minutes so the custard absorbs — the bread should look wet, not dry on top.

4. 4

   Bake 35–40 minutes until puffed, golden on the edges, and the center is set (a knife in the middle should come out mostly clean, no liquid egg). Rest 10 minutes before cutting. You want a sliceable breakfast casserole with custardy bread and savory sausage — not a soggy middle or dry scrambled-egg brick.