Straw-and-hay pasta gets its name from the two different-colored pastas in the recipe. We’re going extra “green” with the sauce.
In a dry small skillet over medium heat (or in a toaster oven on a small tray), toast the pine nuts, stirring occasionally, until golden and fragrant, 3 to 4 minutes.
Bring a large pot of water to a boil for the pastas. Salt the water and add the pastas. Cook for 5 minutes. Reserve 1 cup of the cooking water, then drain.
In a food processor, add half of the spinach, the stock, onion, garlic, and nutmeg; season with salt and pepper. Pulse until well chopped. With the machine running, stream in the oil. Transfer the spinach puree to a large skillet. Bring to a boil, then simmer until thickened, about 5 minutes. Coarsely chop the remaining spinach and wilt into the sauce. Add the pastas and cooking water and simmer, tossing the pastas, until al dente, 3 to 4 minutes more. Add the cream and toss to combine. Remove from heat. Add 1 cup Parm and the lemon juice; season. Serve in shallow bowls and top with more cheese and the toasted pine nuts.