Cauliflower & stilton soup

Heat a knob of butter in a saucepan and gently fry a chopped onion until soft.Add a peeled and diced potatoe along with the florets from a med sized cauliflower.Add 500ml veg stock to the pan.Simmer for 25 mins.Puree with a blender,then return to the pan and add a large splash of milk.Season .Heat until simming,serve sprinkled with a little crumbled stilton.