Breakfast Strata

Instructions

1. Prepare the bread
   Arrange the bread cubes on a large baking sheet and toast in a 350°F (175°C) oven until lightly golden, about 10 minutes. Allow to cool completely while preparing the other ingredients.
2. Sauté the vegetables
   Heat olive oil in a large skillet over medium heat. Add onions and cook until translucent, about 3 minutes. Add mushrooms and bell pepper, cooking until softened, about 5 minutes more. Stir in spinach and cook just until wilted, about 1 minute. Remove from heat and let cool slightly.
3. Create the egg mixture
   In a large bowl, whisk together eggs, milk, cream, Dijon mustard, salt, pepper, and nutmeg until well combined. Stir in 1½ cups of the Gruyère cheese and ¾ cup of the Parmesan cheese.
4. Assemble the strata
   Butter a 9x13-inch baking dish. Place half of the toasted bread cubes in the bottom of the dish. Top with half of the vegetable mixture. Pour half of the egg mixture over the top. Repeat with remaining bread, vegetables, and egg mixture. Press down gently to ensure bread is soaking up the liquid. Cover with plastic wrap and refrigerate for at least 1 hour or overnight.
5. Prepare for baking
   Remove the strata from the refrigerator 30 minutes before baking to bring to room temperature. Preheat the oven to 350°F (175°C). Remove plastic wrap and sprinkle the remaining ½ cup Gruyère and ¼ cup Parmesan cheese on top of the strata.
6. Bake the strata
   Bake uncovered until the strata is puffed, golden brown, and the center is set (a knife inserted in the center should come out clean), about 45-50 minutes. If the top browns too quickly, cover loosely with aluminum foil.
7. Rest and serve
   Allow the strata to rest for 10 minutes before serving. This helps it set and makes it easier to slice. Serve warm, garnished with fresh herbs if desired.