What makes white lasagna so special and totally irresistible is the impossibly creamy white sauce that’s blanketed throughout the casserole.
If creamy pasta makes you weak in the knees, white lasagna is going to be right up your alley. Unlike lasagnas made with marinara, you won’t find a drop of red sauce in sight. Here you get layers of hearty pasta, ricotta, mozzarella, Italian sausage crumbles, and an entire pound of fresh spinach.
But what makes white lasagna so special and totally irresistible is the impossibly creamy white sauce that’s blanketed throughout the casserole. Ready to get cooking?
The white sauce used in this lasagna is béchamel. It’s thick and incredibly creamy, although not too rich or heavy. Béchamel is one of the five building-block sauces in French cuisine, and is made with a roux (equal parts butter and flour) mixed with milk, and seasoned with salt, pepper, and often a pinch of ground nutmeg.
Like all lasagnas, white lasagna is assembled in layers, and you’ll add the white sauce to several places.
Just as with red lasagna, there’s a variety of vegetables and/or meat that can be added to white lasagna. Here, the lasagna is layered with wilted spinach and Italian sausage (take your pick of mild or hot). Spinach adds a nice pop of color and lends freshness to an otherwise hearty casserole. And because it’s packed with seasonings and fat, sausage crumbles give the lasagna even more flavor.
Any cooked vegetable can work in white lasagna, with roasted or grilled veggies being an especially good choice. Just be sure to avoid using raw vegetables, which can lead to a soggy lasagna because of the water content. Shredded or chopped cooked chicken breast can be substituted for the sausage. Or if you want to make a vegetarian white lasagna, the meat can be omitted altogether.
Let 1 quart whole milk sit on the counter until room temperature.
Arrange a rack in the middle of the oven and heat the oven to 400°F. Meanwhile, arrange 15 dry lasagna noodles in an even layer in a 9×13-inch baking dish. Cover the noodles with hot tap water and let soak while you prepare the filling and sauce, about 30 minutes.
If using frozen spinach, thaw 16 ounces according to package directions. Transfer to a clean kitchen towel, roll it up in the towel, and carefully squeeze out all the excess moisture.
Dice 1 medium yellow onion. Mince 3 garlic cloves. Grate 12 ounces low-moisture mozzarella cheese on the large holes of a box grater (about 3 cups). Finely grate 2 ounces Parmesan cheese (about 1 packed cup).
Heat 1 tablespoon olive oil in a large Dutch oven or pot over medium-high heat until shimmering. Add 1 pound uncooked Italian sausage and cook, breaking it up with a wooden spoon, until browned and cooked through, 5 to 7 minutes. Add the onion and garlic, and cook, stirring occasionally, until softened and translucent, about 5 minutes.
If using fresh baby spinach, add 1 pound a few handfuls at a time and stir until just wilted, 3 to 5 minutes. If using frozen spinach, add to pot and cook, stirring occasionally, until the liquid has evaporated, about 2 minutes. If necessary, drain off any liquid. Season with 1/2 teaspoon of the kosher salt and 1/4 teaspoon of the black pepper. Remove the pot from the heat and let cool while you make the béchamel sauce.
Melt 1 stick unsalted butter in a large saucepan over medium heat. Add 1/2 cup all-purpose flour, and cook, whisking constantly, until the paste is bubbling and begins to dry out slightly, about 2 minutes. Gradually whisk in the milk until no lumps remain. Bring to a boil over high heat. Reduce to a simmer, and cook, stirring occasionally, until thickened, 1 to 2 minutes. Add 2 teaspoons of the kosher salt and a pinch of ground nutmeg, and stir to combine. Remove the pot from the heat.
Place half of the Parmesan cheese, 1 container ricotta cheese, the remaining 1/4 teaspoon kosher salt, and remaining 1/4 teaspoon black pepper in a medium bowl and stir to combine. Drain the lasagna noodles.
Assemble the lasagna: Place 1/4 cup béchamel sauce into the baking dish and spread into a thin, even layer. Arrange 5 of the lasagna noodles in an even layer on top of the sauce, breaking them if needed to fit (it’s OK if the noodles overlap slightly). Dollop and spread 1/2 of the ricotta mixture over the noodles. Spoon 1/2 of the sausage and spinach over the ricotta. Sprinkle with 1 cup of the mozzarella. Dollop and spread about 1 heaping cup of the béchamel over the mozzarella.
Repeat layering 5 more lasagna noodles, the remaining ricotta mixture, the remaining sausage and spinach, 1 cup of the mozzarella, and 1 heaping cup of the béchamel. Top with the remaining lasagna noodles, remaining béchamel sauce, remaining mozzarella, and remaining Parmesan.
Bake uncovered until the cheeses are melted and lightly browned, and the sauce is bubbling, about 30 minutes. Let cool on a wire rack for at least 15 minutes before serving.
Make ahead: The lasagna can be assembled and refrigerated unbaked up to 2 days in advance, or frozen for up to 1 month. Thaw the frozen lasagna for 2 days in the refrigerator before baking.
Storage: Leftovers can be refrigerated, tightly wrapped, for up to 3 days.