1. Heat a large nonstick skillet over medium-high heat; add oil. Add onion and garlic; sauté 4 minutes or until onion is tender. Stir in lemon rind.
2. Reduce heat to medium; add mushrooms, and cook 8 minutes or until tender. Sprinkle with salt and pepper.
3. Remove pan from heat, and stir in half-and-half and sherry. Return pan to medium-high heat, and bring to a boil; boil 1 minute or until slightly thickened. Sprinkle with parsley.