Peel avocado. Remove and discard the stone. Scoop avocado flesh into a small food processor. Add sour cream, lemon juice, dried chilli flakes, salt and pepper. Process until it forms a smooth sauce. Transfer to a serving bowl.
Heat a barbeque grill on medium heat. Cut prosciutto in half, lengthways. Trim asparagus. Wrap a strip of prosciutto around each asparagus stalk. Spray with olive oil. Cook asparagus for 3-4 minutes on preheated grill or until browned on all sides. Serve with avocado sauce.