START TO FINISH: 40 minutes
SERVINGS: 4
This ricotta-based pesto gets its pale green hue from an abundance of parsley. Its deep flavor comes from sage that has been gently cooked in olive oil. We used the microwave to make the sage–oil infusion because it does the job quickly. But take care not to overheat the mixture or both the sage and the oil will become bitter. The ideal pasta for this dish is a short, tubular shape with ridges that catch the pesto; we liked rigatoni and penne rigate.
Don’t cook the pasta before preparing the pesto, as the pasta must be hot when tossed with the sauce. Also, don’t forget to reserve 1 cup of the cooking water before draining the pasta; you’ll need to add at least some of it to the pasta and pesto as you toss them together.
6 tablespoons extra-virgin olive oil
⅓ cup chopped fresh sage
3 cups lightly packed fresh flat-leaf parsley
2 teaspoons grated lemon zest
1 ounce finely grated Parmesan cheese (½ cup), plus more to serve
½ cup whole-milk ricotta cheese
Kosher salt and ground black pepper
12 ounces short, tubular pasta with ridges, such as rigatoni or penne rigate
½ cup walnuts, toasted and coarsely chopped
In a small microwave-safe bowl, stir together the oil and sage, making sure the sage is completely submerged. Microwave on high just until the oil is hot and the sage is fragrant, about 1 minute, checking after 30 seconds; it should not sizzle. Cool to room temperature.
In a food processor, combine the sage-oil mixture and the parsley. Process until finely chopped, about 15 seconds. Add the lemon zest and Parmesan and process until well incorporated, about 5 quick pulses. Transfer to a large bowl. Stir in the ricotta, 1 teaspoon salt and ¾ teaspoon pepper.
In a large pot, bring 4 quarts of water to a boil. Add the pasta and 2 tablespoons salt and cook until the pasta is al dente. Reserve 1 cup of the cooking water, then drain the pasta.
Add the pasta to the ricotta mixture and toss to coat, then stir in ½ cup of the reserved cooking water. The mixture should be creamy; if needed, adjust with additional cooking water. Serve sprinkled with walnuts and additional Parmesan.