Cheese Tortellini with Walnut-Parsley Pesto

The best pesto.

Ingredients

• 1 cup walnuts
• 0.5 cup olive oil
• 0.3333333333333333 cup lightly packed flat-leaf parsley leaves
• 4 tablespoons grated Parmesan cheese, divided
• 2 cloves garlic, smashed
• 0.5 teaspoon salt
• 0.25 teaspoon freshly ground black pepper
• 1 pound fresh cheese tortellini
• 1 tablespoon salted butter

Steps

1. Place walnuts, oil, parsley, 3 tablespoons Parmesan cheese, garlic, salt, and pepper in a food processor or blender; pulse into a coarse puree.
2. Fill a large pot with lightly salted water and bring to a rolling boil; stir in tortellini and return to a boil. Cook uncovered, stirring occasionally, until the tortellini float to the top and the filling is hot, 7 to 8 minutes. Drain tortellini, reserving 1/2 cup cooking water.
3. Toss tortellini with 1/4 cup of the reserved pasta water, walnut pesto, and butter. Add more of the cooking water if mixture seems dry. Sprinkle with remaining 1 tablespoon Parmesan cheese and pass more at the table.