Heat 2 tbsp butter in a large soup pan and gently cook 1 medium onion, coarsely chopped, 1 clove garlic, chopped, and 2 large spring onions, chopped until they begin to soften.
Add 3 medium rooster potatoes, peeled and cubed, and stir well to coat.
Add 1.5 litres chicken stock and leave to simmer for 10 minutes.
Meanwhile, remove the peas from their pods.
Add 500 grams fresh garden peas to the soup and simmer for a further 5 minutes.
Add 30 grams lovage and simmer gently for a further 5-10 minutes until all the vegetables are tender.
Transfer the soup to a high speed blender and blend until it reaches a smooth consistency.
Return to the heat and stir in 100 ml double cream. Do not allow to boil.
Serve with lovage leaves scattered across the top.