If creamy pasta makes you weak in the knees, white lasagna is going to be right up your alley. You’ve got to try it! Unlike lasagnas made with marinara, you won’t find a drop of red sauce in sight. Here you’ll find 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?

Ingredients

• 4 cups whole milk
• 1 medium yellow onion
• 3 cloves garlic
• 12 ounces low-moisture whole-milk or part-skim mozzarella cheese (about 3 cups)
• 15 dried lasagna noodles (not no-boil, about 2/3 of a 1-pound box)
• 2 ounces Parmesan cheese (about 1 firmly packed cup grated on a Microplane or 2/3 cup store-bought)
• 1 pound uncooked sweet or hot Italian sausage (chicken, turkey, or pork), casings removed if using links
• 1 stick (1/2 cup) unsalted butter
• 1/2 cup all-purpose flour
• 2 3/4 teaspoons kosher salt, divided
• 1/2 teaspoon freshly ground black pepper, divided
• Pinch ground nutmeg
• 1 tablespoon olive oil
• 1 pound baby spinach, or 1 (16-ounce) package frozen spinach
• 1 (15- to 16-ounce) container whole-milk ricotta cheese (about 2 cups)

Preparation

1. Set 4 cups whole milk at room temperature.
2. 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. 
3. 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).
4. 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.
5. Heat 1 tablespoon olive oil in a large Dutch oven or pot over medium-high heat until shimmering. Add 1 pound Italian sausage and cook, breaking it up with a wooden spoon, until browned and cooked through, 5 to 7 minutes.
6. Add the onion and garlic, and cook, stirring occasionally, until softened and translucent, about 5 minutes.
7. 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.
8. Season with 1/2 teaspoon the kosher salt and 1/4 teaspoon the black pepper. Remove from the heat and let cool while you make the béchamel sauce.
9. Melt 1 stick unsalted butter in a large saucepan over medium heat. Whisk in 1/2 cup all-purpose flour, and cook, stirring constantly until the paste is bubbling and begins to dry out slightly, about 2 minutes.
10. 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.
11. Add the 2 teaspoons kosher salt and a pinch of ground nutmeg and stir to combine. Remove from the heat.
12. 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.
13. Drain the lasagna noodles and set aside. Spread about 1/4 cup béchamel sauce into the baking dish.
14. Arrange 5 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 half of the ricotta mixture over the noodles. Spoon half of the sausage and spinach over the ricotta, then sprinkle with 1 cup of the mozzarella. Dollop and spread about a third of the béchamel sauce (about 1 heaping cup) over the mozzarella.
15. Arrange 5 more noodles over the mozzarella, followed by the remaining ricotta mixture, remaining sausage and spinach, 1 cup of the mozzarella, and 1 heaping cup of the béchamel sauce. Top with the remaining 5 noodles and the remaining béchamel sauce. Sprinkle with the remaining 1 cup mozzarella and Parmesan.
16. 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.

RECIPE NOTES

Leftovers can be refrigerated, tightly wrapped, for up to 3 days.

• 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.