Spring Strata with Asparagus, Leeks, Sausage, and Cheese

Ingredients

• 1 pound white bread loaf, cut into 1 1/2-inch cubes
• 5 tablespoons vegetable oil, divided
• 1 large leek, white and pale green parts only, diced
• 2 medium cloves garlic, thinly sliced
• 1 pound asparagus, woody ends trimmed and asparagus cut into 1-inch lengths
• Kosher salt and freshly ground black pepper
• 1/2 pound cremini mushrooms, trimmed and sliced
• 1 pound Italian sausage, casings discarded
• 8 ounces Gruyère cheese, 6 ounces diced and 2 ounces grated, divided
• 2 tablespoons minced flat-leaf parsley
• 1 teaspoon minced fresh thyme leaves
• 10 large eggs
• 2 1/2 cups milk

Directions

1. Set the oven racks in the lower-middle and upper-middle positions, then heat the oven to 275 degrees F. Divide the bread cubes between 2 rimmed baking sheets in an even layer. Place the pans on the racks and bake for about 35 minutes, stirring the cubes and switching the pans around a few times, until the bread is largely dried out. Take the pans out of the oven and let the bread cool.
2. While the bread dries, warm 2 tablespoons (30ml) oil in a large skillet over medium-high heat until it glints. Add the leek and garlic, then cook, stirring, until they begin to soften, 1 to 2 minutes. Stir in the asparagus, add salt and pepper, and cook until it is tender but still has a little snap, about 3 minutes. Transfer the vegetables to a large mixing bowl, then clean out the skillet.
3. Return the skillet to medium-high heat and add the remaining 3 tablespoons (45ml) oil. Once the oil is hot, add the mushrooms and cook, stirring, until their moisture cooks off and they begin to take on color, about 6 minutes. Add the sausage and cook, breaking it into small bits with a spatula or spoon, until no longer raw, about 5 minutes. Add this mixture to the bowl with the asparagus, then stir in the cubed cheese, parsley, and thyme.
4. Whisk the eggs and milk together in a medium bowl until smooth and fully blended.
5. Put the dried bread into the bowl with the asparagus and sausage mixture. Pour the egg mixture over everything, season with salt and pepper, and stir until evenly combined. Spoon it all into a 9- by 13-inch baking dish, cover the dish with plastic, and chill for at least 1 hour and up to overnight.
6. When it is time to bake, heat the oven to 325 degrees F. Uncover the baking dish and bake the strata until the eggs are set all the way through the middle, about 35 minutes. Scatter the grated cheese over the top, switch on the broiler, and place the dish on the top rack just until the cheese melts and the surface is lightly browned in places, about 2 minutes. Serve.