Cook the penne to packet directions. Five minutes before the end of cooking time, increase the heat and add the peas to the penne. Cook until the penne and peas are cooked. Drain well, reserving ¼ cup of cooking liquid. Add enough cooking liquid to the penne to just moisten. Mix the pesto through the penne and peas. Sprinkle over parmesan cheese and garnish with basil leaves.