Strain and leave om a bowl. Add the butter or oil and sweet off the onionfor 4-5 mins. Need to be cooked but not browned. then add the garlic and cook 2 more mins.

Add the milk and return the asparagus and pototo and 1/2 sotck cube and heat until just simmers. then carefully using a hand blender blitz until smooth. Get a 2nd pan with a seive over the top and push the soup through using the back of a spoon and discard the hard bits.