How to Make It
Heat oil in a deep 12- to 14-inch skillet over medium-high until shimmering. Add lamb, and season with 1/2 teaspoon salt and 1/2 teaspoon pepper. Cook, breaking up meat with a spoon, until fat has rendered and meat is browned, 6 to 8 minutes. Using a slotted spoon, transfer lamb to a bowl, and set aside. Spoon off and discard all but 1 tablespoon rendered drippings from skillet.
Reduce heat to medium, and add onion, harissa, garlic, remaining 1/2 teaspoon salt, and remaining ¼ teaspoon pepper. Cook, stirring occasionally, until onion is softened, about 8 minutes. Stir in spinach until just wilted, 1 to 2 minutes. Stir in lasagna noodles, marinara, stock, and reserved lamb (it’s OK if noodles aren’t completely submerged). Bring to a simmer over high; reduce heat to medium-low, cover, and cook until pasta is al dente and most of sauce is absorbed, 20 to 25 minutes, stirring once after 10 minutes.
Dollop ricotta over lasagna, and sprinkle with Parmesan. Cover and cook over medium-low until cheese is hot and melted, about 5 minutes. Garnish with parsley and additional Parmesan. Serve with a big green salad and garlic bread.