Thaw shrimp according to package directions and peel if needed; rinse and set aside
Saute chopped onion and garlic in olive oil until limp (about 5 minutes)
Add marinara sauce, wine and a little water if needed and let simmer for 10 minutes
Add shrimp and bring to low boil, then reduce heat and let simmer for 15 minutes
Remove from heat and add half and half, stirring well. Add basil, salt and pepper and let simmer about 5 more minutes.
Serve over penne pasta