Spinach Sourdough Strata

A strata is simply a savory bread pudding. This dish is versatile and you can use any kind of cheese or vegetables you have on hand. If you don’t have sourdough bread, just use regular Italian white bread. Toss in cooked sausage or crumbled bacon if you wish. It’s perfect for a weekend brunch or potluck. Assemble the night before and pop it in the oven first thing in the morning.

1 bag chopped frozen spinach, thawed, excess liquid squeezed out
4 tablespoons butter
1 large yellow onion, chopped, about 2 cups
8 cups stale sourdough bread cubes (1 inch or smaller cubes)
2 cups grated Gruyère cheese
1 heaping cup grated sharp cheddar cheese
10 large eggs
4 cups whole milk
2 tablespoons Dijon mustard
1 teaspoon salt
½ teaspoon, or more, freshly ground black pepper
¼ teaspoon ground nutmeg

1. Melt the butter in a heavy skillet over medium heat. Add the onion and cook, stirring frequently, until soft and lightly browned, about 8 minutes. 
2. Spray a 9×13-inch baking dish with cooking spray. Spread about one third of the bread cubes in the dish and top evenly with about 1/3 of the spinach and 1/3 of the onions, followed by 1/3 of the cheese. Make sure there are no dense clumps of spinach. Repeat the layers, ending with cheese.
3. In a large bowl, whisk together the eggs and add the mustard, milk, salt, pepper, and nutmeg; whisk until well combined. Pour the custard mixture evenly over the strata. Cover with plastic wrap and refrigerate for at least 1 hour or overnight to let the egg mixture soak into the bread cubes.
4. Preheat oven to 350°F. Bake, uncovered, until puffed, golden, and set in the middle, about 45 minutes. Let stand 5 minutes before serving.