Heat the olive oil in a saucepan and gently sauté the garlic and spring onion for a minute.
Meanwhile, remove the woody ends of the asparagus.
Chop the asparagus into 3 cm pieces and add to the pan, together with the peas.
Stir for a few seconds, then add the stock. Bring to the boil and cook for 5 minutes.
Turn off the heat and add the watercress. Put a lid on and rest for 2minutes.
Using a spoon, take out a few asparagus tips for decoration.
Using a hand-held blender, purée it until you get a smooth, silky soup. Add more stock if it’s too thick. Reheat if necessary.
Garnish with the asparagus tips and serve with a squeeze of lemon juice or a drop of cider vinegar and plenty of ground pepper.