To make the pesto, combine the arugula, walnuts, parmesan cheese, garlic, salt and pepper in a food processor. With the food processor running, slowly add the olive oil until the mixture is your desired consistency. You can make it as thin or thick as you like.

To prepare the pasta, bring a large pot of salted water to a boil. Add the capellini or angel hair pasta and cool until al dente.

Drain the pasta, reserving 1 cup of the pasta water. Toss the pasta with a few tablespoons of the pesto. Add pasta water if necessary to moisten the pesto. Add the ricotta cheese and toss until incorporated.

Serve immediately. Garnish with arugula, if desired.