Directions

1. Preheat the oven to 425 ̊F. Brush the olive oil on the cut sides of the squash and place cut-side down on a baking sheet. Roast until soft and turning brown in some spots, 35 to 40 minutes. Scoop out the flesh into a small bowl and mash with a fork.

2. Heat a large skillet over medium heat, add 1 tablespoon of olive oil. Next, add the sausage and cook, breaking up the meat with a wooden spoon, until no longer pink, about 5 minutes. Remove sausage with a slotted spoon to a medium size bowl.
3. Add 2 tablespoons of olive oil to the skillet. Add the onion, sage, a sprinkle of salt, and a few grinds of pepper. Cook, over medium-low heat, stirring occasionally for 10 minutes. Add the jalapeno and continue to cook until the onion is softened and caramelized, 10 to 15 minutes more. Add to the bowl with the sausage.

4. While the onions cook, prepare the bechamel sauce: Melt the butter in a saucepan over medium heat. Add the flour and whisk for 1 minute. Gradually whisk in the milk. Bring to a boil over medium-high heat. Then reduce the heat to medium and simmer until the sauce thickens slightly, whisking often, about 5 minutes. Stir in the thyme leaves, taste, and season with salt & pepper, if required. Remove from the heat and whisk in ricotta until smooth. Let stand 10 minutes.

5. Position the rack in the center of the oven and preheat to 375 ̊F.
6. Lightly butter a 9" x 13" rectangular baker. Spread 3/4 cup of the bechamel sauce over the prepared baking dish. Arrange lasagna noodles to completely cover the bottom of the baker. Spread 1/4 of the squash puree over the noodles. Sprinkle with 1/2 cup of mozzarella cheese, then drizzle 3/4 cup of bechamel over the cheese. Next arrange another layer of lasagna noodles. Spread 1/4 of the squash puree over the noodles. Then sprinkle the sausage mixture evenly over the puree. Top with 1/2 cup of mozzarella cheese, then drizzle 3/4 cup of bechamel over the cheese. Repeat layering noodles, puree, mozzarella, bechamel, two more times.
7. If cooking immediately, tightly cover the baking dish with lightly greased aluminum foil and bake the lasagna for 40 minutes. Remove the foil, sprinkle the remaining ½ cup of mozzarella and the Parmesan cheeses over the lasagna. Continue baking uncovered until the sauce bubbles and the top is golden, about 15 minutes longer. Let the lasagna stand for 15 minutes before serving.
8. You can prepare lasagna up to 24 hours before baking it. Assemble the lasagna as above, before cooking it, tightly cover the baking dish with lightly greased aluminum foil and in and refrigerate. When you are ready to cook the lasagna, preheat the oven to 375 ̊F. Bake the lasagna for approximately 60 minutes (due to its cold temperature, lasagna that has been stored in a refrigerator requires a slightly longer cooking time). Remove the foil and finish as above.