The combination of mint, scallions, and asparagus makes this dish perfect for spring. You could also spread this pesto on top of chicken breasts or a firm-fleshed fish (anything from cod to salmon would work) and roast, or use it as a spread on sandwiches or crostini.
Make the pesto
Put the scallions, Parmigiano, pine nuts, and mint in a food processor and process until finely chopped. With the processor on, pour the oil down the feed tube in a steady stream, so the mixture thins into a slightly loose paste. Add more oil if needed. Add 1/2 tsp. salt and 3/4 tsp. pepper and pulse once more.
Make the pasta
Bring a large (6-quart) pot of well-salted water to a boil over high heat. Add the pasta and cook, stirring occasionally, until nearly tender, about 2 minutes less than the package timing. Add the asparagus and cook with the pasta until both are tender, about 2 minutes more. Drain well and toss with the pesto and lemon juice. Add more lemon juice, salt, and pepper to taste. Serve sprinkled with black pepper and the Parmigiano.
Make Ahead Tips
The pesto will keep in an airtight container in the refrigerator for up to four days.