Step 1Place basil and garlic in bowl of food processor or in blender. Process until basil is minced very fine. With food processor running, add oil very slowly. Stop machine when all oil is absorbed. Add Parmesan and salt and pepper to taste. Process just until cheese is absorbed. Add pine nuts and process so that they are coarsely chopped. Using a rubber spatula, remove pesto from processor. If not using right away, place in an airtight container in refrigerator. Bring pesto back to room temperature before using it.
Step 1Heat broth over medium heat until very hot. Reduce heat to low and keep broth hot.
Step 2Heat oil in large skillet over medium heat. Add onion and cook until it is tender. Add rice to onions and oil, and, stirring constantly, saute until grains of rice are opaque and make a clicking sound against metal of saucepan, 1 minute. Add wine to rice, if desired, and cook slowly, stirring constantly, until it is completely absorbed. Add tomato sauce to rice, stir well and begin to cook rice slowly over low heat. Add hot broth to tomato-tinted rice mixture 1 ladle at a time, stirring frequently. The rice should cook very slowly over low heat. Wait until all liquid is absorbed before adding next ladle of broth.
Step 3When risotto is just tender to the bite, 40 to 45 minutes, remove pan from heat. Add butter and Parmesan cheese and stir vigorously until butter and cheese are absorbed and texture thickens and becomes creamy. Serve in separate bowls. If desired, drizzle pesto sauce into rice. (Or add a bit of chopped fresh mozzarella to each bowl of rice and allow your guests to stir cheese into rice.) Serve immediately with additional grated Parmesan cheese at the table.