Watercress Butter

• 2-3 tablespoons finely chopped watercress
• ¼ pound butter
• lemon juice

Wash watercress very carefully, removing stalks and any discoloured leaves; chop finely. Dry chopped watercress in a cloth and pound it in a mortar with butter. Season to taste with lemon juice, salt and freshly ground black pepper. Chill.