Add the asparagus ends to the stock and bring to the boil, simmering for about 15 minutes, then strain. Heat the butter in a pan, add the remaining asparagus and cook for five minutes.
Stir in the peas and the strained stock, bring to the boil and simmer for five to ten minutes until the vegetables are tender. Liquidise in a blender until smooth then return to the pan.
Add the single cream and reheat gently without boiling. Season and stir through the parsley before serving.