Cheese Tortellini with Walnut Pesto

This comes from my friend Emily who I think got the recipe from Whole Foods.

Cheese Tortellini with Walnut Pesto

1 cup walnuts
1/3 cup lightly packed flat-leaf parsley (with thick stems removed)
2 cloves garlic, smashed
3 TBS grated Parmesan cheese (plus for serving)
1/2 cup olive oil
1/2 tsp salt
1/4 tsp black pepper
1 pound frozen or fresh cheese tortellini it's also good with spinach or whole wheat tortellini)
1 TBS butter

In food processor, pulse the walnuts, parsley, garlic, Parmesan, oil, salt and pepper to a coarse puree.

In a large pot of boiling, salted water, cook the tortellini until just done (12 min. for frozen).

Toss pasta with pesto and the butter (I omit the butter). If the pasta seems dry, add some of the pasta water. Sprinkle with additional Parmesan and pass more at the table. Enjoy!