Roughly chop the sweet onion and gently glaze in a little olive oil (don’t burn it).
Add 500ml of water, salt and the stockcube. Bring to the boil and add the peas and asparagus.
Cook for 10 minutes and taste to be sure that the vegetables are cooked but retain their green colour.
Keep back a few peas and asparagus heads for decoration later.
Pour everything else carefully into a blender and whizz until smooth.
Pour back into the pot and add half a tub of cream, salt and pepper to taste.
Pour the soup into a big bowl or individual plates, pour a little olive oil on the surface and add the peas and asparagus heads, as well as the parsley.
If serving cold let it cool down and put it in the fridge for an hour before serving.