In a large pot, pour in your vegetable or chicken stock. Heat over medium-high heat until it simmers, about 5 minutes.

Add the chopped butter lettuce, sliced spring onions, and fresh dill to the pot. Stir gently, allowing the greens to wilt for around 5 minutes.

Remove half of the mixture to a blender, add the sour cream, and blend until smooth, then return to the pot.

Stir in the lemon juice, then season with salt and pepper. Cook over low heat for another 2-3 minutes.

Ladle the soup into bowls while hot. Optionally garnish with croutons or leftover roast meat.