Broil peppers until charred on all sides. Place in closed paper bag and let stand 10 minutes. Remove skin, seeds and membranes and chop. Heat oil and butter and saute onion and garlic until tender. Add peppers and broth and simmer, uncovered, for 15 minutes. Transfer to blender container and puree. Season with salt and pepper, then add basil and cream. Heat gently, but do not boil. Pour over pasta. NOTE: When the budget allows, stir cooked shrimp or crabmeat into red pepper sauce.