Using a large, deep-sided skillet, cook meatballs in 2 tablespoons olive oil over medium-high heat until browned on all sides. Reduce heat, cover and simmer until internal temperature reaches at least 165ºF. Remove meatballs from skillet.
Combine remaining 3 tablespoons oil, basil, garlic, 3 tablespoons Parmesan cheese, walnuts and lemon juice in food processor or blender. Pulse until finely minced.
Cook orzo according to package directions; drain.
Meanwhile, sauté onion for 3 minutes over medium-high heat using same skillet meatballs were cooked in. Add asparagus; sauté 3 minutes.
Whisk together milk and flour. Add milk to onion and asparagus; cook and stir until just starts to thicken. Stir in pesto and heavy cream until well blended.
Stir in meatballs, orzo and peas; continue cooking until heated through. Remove from heat and stir in remaining 1/2 cup Parmesan cheese.