In a large pot, gently heat 4 cups of vegetable or chicken stock over medium heat until steaming but not boiling, about 5 minutes.

Add 4 cups of chopped butter lettuce and 2 sliced spring onions to the pot. Sauté these vegetables in the warm stock for about 5 to 7 minutes.

Carefully scoop half of the sautéed mixture into a blender, adding ½ cup of sour cream. Blend until smooth and creamy.

Return the blended soup mixture to the pot, stirring gently to combine with the remaining sautéed vegetables. Add the juice of half a lemon and season with salt and pepper.

Increase the heat slightly and let the soup simmer gently on low for another 5 minutes.

Ladle the soup into bowls and garnish with fresh dill or chives. Serve with crusty bread or a light salad.