You will need
Put the diced potato and stock into a medium saucepand and bring to the boil. Simmer gently for 10-15 minutes until the potato is cooked.
Pour this mixture into a blender, add the drained asparagus and puree until smooth. Return to saucepan, stir in milk and reheat thoroughly
Season to taste
Just before serving stir in the soured cream and Gruyere cheese.
cooking for one or two