Bring a large pot of salted water to a boil. Add in the pasta and cook until al dente according to package instructions. Remove two cups of the pasta water, drain the pasta, and set aside.
In a large skillet, heat the oil over medium-high heat and add in the diced onion. Cook until the onion is soft and translucent, about 3-4 minutes. Add in the peas and a splash of pasta water. Cook until the peas have softened, about 1-2 minutes.
Remove half of the peas and place in a bowl with an immersion blender or food processor, along with one cup of reserved pasta water. Blend the pea mixture until smooth and add back to the skillet along with the salt and pepper.
Add in the cooked pasta and parmesan cheese. The sauce should have a thick and creamy consistency but if it’s too thick you can loosen it with a splash of pasta water. Serve immediately with more cheese sprinkled on top.
Notes
Choose a small pasta shape. Any small variety will work well, but try to pick one that’s close in size to the peas like shells, macaroni, or ditallini.
Pasta e Piselli can be served either soupy or thick and saucy. Adjust the thickness by adding a bit more water to reach your preferred consistency.
You can use an immersion blender or food processor fitted with a blade attachment. A regular blender works too; just keep in mind you may need to add a touch more water.
Change up the flavor of this recipe by adding pancetta, cooked bacon, lemon juice, or garlic.
Store leftovers in an airtight container in the refrigerator for up to three days. Reheat with a splash of water and more cheese.