Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until al dente, following package instructions, then drain and set aside.
While the pasta cooks, combine basil leaves, garlic, Parmesan, and olive oil in a food processor or blender. Blend until smooth and bright green, scraping down the sides as needed. Adjust seasoning with salt and pepper.
12 ounces pasta (penne or spaghetti)
Heat a sauté pan over medium heat. Add the shredded cooked chicken and cook until heated through, about 2-3 minutes, stirring occasionally.
12 ounces pasta (penne or spaghetti)
Reduce the heat to low and add the cooked pasta to the pan with chicken. Pour the pesto sauce over the pasta and toss everything together until evenly coated, about 1-2 minutes. The sauce should cling nicely to the pasta without pooling.
12 ounces pasta (penne or spaghetti)
Transfer the pasta to serving bowls. Garnish with additional Parmesan and basil if desired. Serve immediately, enjoying the bright green color and fragrant aroma.