Ingredients

For bolognese sauce:
1/4 cup olive oil
3 ounces sliced pancetta, finely chopped
1 medium onion, finely chopped
1 large carrot, finely chopped
1 celery rib, finely chopped
2 garlic cloves, chopped
2 pounds ground beef chuck (not lean)
1 1/2 cups dry white wine
1 1/2 cups whole milk
1/4 cup tomato paste
1 1/2 teaspoon thyme leaves
For Ricotta filling:
2 (10-ounce) packages frozen chopped spinach,thawed
2 (15-ounce) containers whole-milk ricotta
4 large eggs, lightly beaten
1/2 cup grated Parmigiano-Reggiano
1/2 teaspoon grated nutmeg
3/4 cup whole milk, divided
For assembling lasagne:
12 Barilla no-boil dried lasagne noodles (from 1 box)
1/2 cup grated Parmigiano-Reggiano

Directions

1. Make Sauce: heat oil in a 12-to 14-inch heavy skillet over medium heat until it shimmers. Cook pancetta, onion, carrot, celery, and garlic, stirring occasionally, until vegetables are golden and softened, 12 to 15 minutes.
2. Add beef and cook, stirring occasionally and breaking up any lumps, until meat is no longer pink, 6 to 10 minutes.



3. Stir in wine, milk, tomato paste, thyme, 1/4 teaspoon salt, and 3/4 teaspoon pepper. Simmer, uncovered, stirring occasionally, until most of liquid has evaporated but sauce is still moist, about 1 hour.



4. Make ricotta filling: put spinach in a kitchen towel (not terry cloth) and twist to squeeze out as much moisture as possible.
5. Whisk together ricotta, eggs, parmesan, nutmeg, 1 1/4 teaspoons salt, and 1 teaspoon pepper.



6. Transfer 1 1/2 cups ricotta mixture to another bowl and whisk in 1/4 cup milk; set aside.
7. Whisk spinach into remaining filling with remaining 1/2 cup milk.
8. Assemble and bake lasagne: preheat oven to 375°F with rack in middle.
9. Soak noodles in a bowl of very warm water until pliable but not softened, 3 to 5 minutes. Place on a kitchen towel (it's not necessary to pat noodles dry).
10. Spread 1 1/2 cups bolognese sauce in baking pan and sprinkle with 1 tablespoon parmesan. Cover with 3 noodles, leaving space in between.
11. Spread half of spinach filling on top, then 1 cup bolognese sauce, and top with 1 tablespoon parmesan and 3 noodles; repeat.



12. Top with remaining bolognese sauce, 1 tablespoon parmesan, and remaining 3 noodles. Pour reserved ricotta mixture over top and sprinkle with remaining 1/4 cup parmesan.
13. Cover pan tightly with parchment paper and foil (or just buttered foil) and bake 50 minutes.
14. Remove foil and bake until top is browned in spots, about 15 minutes more. Let stand 15 to 30 minutes before cutting.

Serves 8-10.

Make ahead: Bolognese sauce can be made 2 days ahead and chilled (covered once cool). Lasagne can be made 1 day ahead and chilled. Reheat in a 350°F oven, loosely covered with foil.