2tablespoonpine nuts17g, toasted (can be prepared ahead)
Set the pasta to cook in a pot of boiling water according to packet instructions. Keep a note of cooking time and when you start it so you put peas in at the right time.
Mix together all of the sauce ingredients in a small bowl (mascarpone, lemon zest and juice, parmesan and a little black pepper). Set aside.
If using fresh peas, add them to the pot with the pasta when it has roughly 3 minutes to go. If using frozen, add them about a minute before the end. If your spinach leaves are large, roughly chop them.
Once the pasta is cooked, remove some of the pasta cooking water (around ¼-1/2 cup) then drain the pasta and peas.
Add the spinach to the pasta in the pot and stir to start wilting a little with the heat of the pasta and pot. Add the mascarpone sauce and some of the reserved pasta water (start with around 2-3 tablespoons), pouring the hot water over the spinach as much as possible to help it wilt further. Stir and add a little more water as needed until you get the consistency you like.
Serve topped with the toasted pine nuts (and extra parmesan, as you prefer).
I used casarecce pasta here, but bucatini and linguini would also be a good fit. Bow tie would also be good, but use as you have/prefer.