Pasta Primavera With Asparagus and Peas

sugar snap peas, stems trimmed

asparagus, ends snapped

unsalted butter

fresh English peas

thinly sliced spring onion, white part only (or use shallot)

garlic cloves, finely chopped

fine sea salt, more as needed

Black pepper, more as needed

fettuccine or tagliatelle, preferably fresh (see recipe)

grated Parmigiano-Reggiano, at room temperature

crème fraîche or whole milk Greek yogurt, at room temperature

finely chopped parsley

finely chopped tarragon