Ingredients
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1 (10 ounce) package frozen spinach, thawed
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3 tablespoons unsalted butter
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1 teaspoon salt
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1/2 teaspoon black pepper
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1/4 teaspoon nutmeg, freshly grated
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8 cups French bread (1/2 lb) or 8 cups Italian bread, in 1 inch cubes (1/2 lb)
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6 ounces gruyere, coarsely grated (2 cups)
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2 ounces parmigiano-reggiano cheese, finely grated (1 cup)
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2 3/4 cups milk
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9 large eggs
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2 tablespoons Dijon mustard
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1 1/2 cups onions, finely chopped (1 large)
Instructions
- Squeeze handfuls of spinach to remove as much liquid as possible, then finely chop.
- Cook onion in butter in a large heavy skillet over moderate heat, stirring, until soft, 4 to 5 minutes.
- Add 1/2 teaspoon salt, 1/4 teaspoon pepper, and nutmeg and cook, stirring, 1 minute.
- Stir in spinach, then remove from heat.
- Spread one third of bread cubes in a buttered 3-quart gratin dish or other shallow ceramic baking dish and top evenly with one third of spinach mixture.
- Sprinkle with one third of each cheese.
- Repeat layering twice (ending with cheeses).
- Whisk together milk, eggs, mustard, and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper in a large bowl and pour evenly over strata.
- Chill strata, covered with plastic wrap, at least 8 hours (for bread to absorb custard).
- Preheat oven to 350°F.
- Let strata stand at room temperature 30 minutes.
- Bake strata, uncovered, in middle of oven until puffed, golden brown, and cooked through, 45 to 55 minutes.
- Let stand 5 minutes before serving.
- note: Strata can be chilled up to 1 day.
- Let stand at room temperature 30 minutes before baking.