Cream of Asparagus Soup

Steps

1. Rinse the asparagus. Bend each spear near the base: it snaps on its own where the woody part begins. Keep the ends. Cut off the tips 1 1/2 inches (4 cm) long and set them aside. If the spears are thicker than a pencil, peel the lower third with a vegetable peeler and keep the peelings with the ends.
2. Put the ends and peelings in a saucepan with the vegetable broth. Bring to a simmer and let steep, covered, for 15 minutes. Strain, pressing on the ends with the back of a ladle, then discard them: you're left with about 1 liter of broth that tastes of asparagus.
3. While the broth steeps, bring a small pan of water to a boil with 1/2 teaspoon of the salt. Drop in the tips for 2 minutes, then move them to a bowl of ice water to set their green color. Drain them on a kitchen towel.
4. Split the white part of the leek lengthwise, rinse it under running water while fanning the layers to wash out any grit, then slice it thin. Peel the potato and cut it into 1/2-inch (1 cm) cubes. Cut the asparagus stalks into 3/4-inch (2 cm) pieces.
5. Melt the butter in a Dutch oven over medium-low heat. Add the leek and a pinch of salt and sweat it for 6 to 8 minutes, stirring: it should turn translucent and soft without taking on any color, or the soup will turn beige.
6. Add the potato and the strained broth, bring to a boil, then simmer for 10 minutes, until the potato crushes under a spoon. Add the asparagus pieces and cook 7 to 8 minutes, no more: the tip of a knife slides through with no resistance and they're still bright green.
7. Take the pot off the heat, add 120 ml of the cream, and blend in a blender for 1 to 2 minutes, until perfectly smooth. Don't fill the jar more than halfway and hold the lid down with a towel: the steam pushes up. Then pass the soup through a fine-mesh strainer, pressing with a ladle.
8. Return the pot to low heat without letting it boil. Season with the rest of the salt and the white pepper. Add the lemon juice just before serving and taste: it should wake the soup up without making it sour. If it's too thick, loosen it with a little hot water.
9. Ladle into warm shallow bowls. Arrange the asparagus tips in a star in the center, drizzle the remaining cream from the tip of a spoon, and serve right away.