Parsley Walnut Pesto

1/4 cup walnuts (3/4 oz)
1 clove garlic,
1 1/3 cups packed fresh flat-leaf parsley
3 tablespoons extra-virgin olive oil
2 1/2 tablespoons finely grated Pecorino
1 tablespoon water
1 teaspoon salt
1/4 teaspoon black pepper
1/4 teaspoon finely grated fresh lemon zest

Toast nuts in a dry small heavy skillet over moderate heat, stirring frequently, until fragrant and a shade darker, about 6 minutes, then cool completely.

Pulse nuts and garlic in a food processor until finely ground. Add parsley, oil, cheese, water, salt, pepper, and zest and pulse until parsley is coarsely chopped.

Makes 4 servings