Cream of lettuce soup

Ingredients:

• 4 tablespoons unsalted butter
• 1/4 cup flour
• 1 medium onion, chopped
• 4 cups of milk
• 1 head of romaine lettuce (350 g), cut into pieces, plus shredded leaves for serving

Preparation:

1. In a large saucepan over medium heat, melt the butter. Add the flour, onion, 1 3/4 teaspoons of salt, and a couple of turns of black pepper and cook until the onion is softened, about 6 minutes. Stir in the milk and simmer for 10 minutes. Add the lettuce leaves and cook, tossing with tongs, until bright green, about 1 minute.
2. Blend the soup in batches until smooth. Return it to the pan, reheat, and thin with milk or water if needed. Serve garnished with shredded lettuce.
   
   
   When blending hot liquid, let it cool for about five minutes first, then pour it into a blender, filling it only halfway. Replace the lid, leaving it slightly ajar and covering it with a kitchen towel to prevent splashes.