To make the pesto, process the basil, garlic, salt, walnuts and Parmesan until the leaves are coarsely chopped. With the machine running, add about 6 tablespoons olive oil (more as needed) until the mixture is smooth, but still somewhat paste-like. Taste and adjust seasoning. Set aside.
Meanwhile, cook the pasta according to package directions in salted boiling water. Reserve 1 cup of the pasta cooking water and drain the rest. Leave the pasta in the pot. Stir in the tomatoes, olives and desired amount of pesto and heat through. If the mixture seems too dry, moisten with a little reserved pasta cooking water or more pesto.
To serve, warm pasta bowls, add pasta, top with the fresh mozzarella pearls and garnish with pepper and basil leaves.
Nutrition information per serving:
Calories542Fat32 gSodium610 mg
Carbohydrates50 gSaturated fat6 g