Prep Time: PT10M
Cook Time: PT9H50M
Total Time: PT10H
Yield: 8 to 10 servings
This make-ahead breakfast casserole combines fresh spinach and creamy Gruyère cheese for a hearty vegetarian dish. Prep it the night before and wake up to a golden, puffy casserole that's perfect for holiday mornings or weekend brunches with family.
Casserole Ingredients
- 8 ounces - baguette or other crusty bread, cut into 1 ½-inch cubes
- 6 tablespoons - unsalted butter
- 1 teaspoon - kosher salt (such as Diamond Crystal), more as needed
- 2 - leeks, trimmed, halved and thinly sliced into half-moons
- 10 ounces - fresh spinach
- 1/4 teaspoon - grated nutmeg
- Large pinch - ground cayenne
- 1 teaspoon - finely grated lemon zest
- 2 tablespoons - dry vermouth or white wine
- 8 - large eggs
- 2 cups - half-and-half (or use a mix of milk and heavy cream)
- 1/2 teaspoon - freshly cracked black pepper
- 4 ounces (2 cups) - Gruyère, grated
- 3/4 cup - grated Parmesan
- Step 1 Heat oven to 350 degrees. Lightly butter a 9-by-13-inch baking dish or a large gratin dish, ensuring an even coat to prevent sticking.
- Step 2 Spread the bread cubes on a baking sheet in a single layer. Bake until crisp, approximately 8 to 10 minutes. Transfer the cubes to a large bowl and toss with 4 tablespoons of melted butter and a pinch of salt until completely coated.
- Step 3 In a large sauté pan, melt the remaining 2 tablespoons of butter over medium-high heat. Introduce the leeks with a pinch of salt, and sauté until they are tender and gently golden, about 5 minutes.
- Step 4 Incorporate about half of the spinach, a pinch of salt, nutmeg, cayenne, and lemon zest. Stir until the spinach wilts, roughly 2 to 4 minutes. Add the remaining spinach and another pinch of salt, cooking until most of the liquid has evaporated, an additional 5 minutes. Stir in the vermouth or white wine and cook for 2 to 4 minutes, until the pan appears dry. Adjust seasoning if necessary, and let the mixture cool.
- Step 5 In a medium bowl, whisk together the eggs, half-and-half, pepper, and 1 teaspoon of salt. Pour this custard over the bread cubes, tossing thoroughly to coat. Incorporate the spinach mixture, 1¾ cups of Gruyère, and ½ cup of Parmesan. Mix until evenly combined, using your hands if necessary for better integration.
- Step 6 Transfer the mixture into the prepared baking dish, cover, and refrigerate for at least 8 hours or overnight, allowing the flavors to deepen.
- Step 7 When ready to bake, preheat the oven to 350 degrees. Uncover the casserole and sprinkle the remaining ¼ cup of Gruyère and ¼ cup of Parmesan on top. Bake for 50 to 60 minutes, or until the center is set and firm, and maybe slightly puffy. Allow it to rest for 10 to 20 minutes prior to serving.