Kale & sausage lasagna with pumpkin béchamel

Butter	4 tablespoons
Flour	6 tablespoons
Milk, hot	4 cups
Salt	¼ teaspoon
Pepper, white, freshly ground	¼ teaspoon
Nutmeg, freshly ground	Pinch
Pumpkin, pureed	2 cups
Lasagna noodles	15
Oil, olive	2 tablespoons
Sausage, sweet Italian, chopped	1 ½ pounds
Kale, stems removed, chopped	8 cups
Garlic, minced	8 cloves
Red pepper, crushed	¼ teaspoon
Ricotta	1 pound
Eggs	2 large
Sage, fresh, finely chopped	2 tablespoons
Mozzarella, shredded or sliced	2 cups
Parmesan, finely shredded	¼ cup

1. Preheat the oven to 375°F. 
2. Melt the butter in a medium saucepan over medium heat, then stir in the flour with a wooden spoon to make a smooth, somewhat loose paste.
3. Continue stirring until the butter and flour foam together for 2 minutes without coloring more than a buttery yellow; remove from heat. 
4. When the bubbling stops, pour in the hot milk all at once, whisking vigorously to blend thoroughly. 
5. Continue whisking slowly over moderately high heat, scraping along the bottom and sides of the pan, until the sauce comes to a simmer; simmer 2 to 3 minutes, stirring with a wooden spoon. 
6. Stir in the salt, white pepper, nutmeg, and pumpkin. 
7. Simmer until the sauce is thick enough to coat the back of a spoon. 
8. Bring a pot of salted water to a boil, add the pasta, and cook for 6 minutes; drain, and set aside. 
9. In a cast-iron skillet, heat the oil over medium heat. 
10. Add the sausage and cook through, until all the pink is gone, stirring occasionally; drain all but 2 tablespoons of the fat. 
11. Add the kale and garlic, stirring to coat; cook until wilted, add the red pepper, then set aside. 
12. In a small bowl, combine the ricotta, eggs, and sage; set aside. 
13. To assemble, spoon 1 cup of béchamel to the bottom of a 9-by-13-inch pan; cover by layering 4 to 5 noodles lengthwise. 
14. Spread half of the ricotta mixture over the noodles, followed by half of the kale-sausage mixture, cover with 1-cup mozzarella, and then pour 1-cup béchamel over the cheese. 
15. Add another layer of noodles, remaining ricotta mixture, kale-sausage mixture, and mozzarella. 
16. Top with the last layer of noodles, pour the remaining béchamel over the top, and then sprinkle with parmesan evenly. 
17. Bake for 45 to 50 minutes, or until the top is golden brown.
18. Let rest 15 minutes before serving. 

Recipe from Food52.com.