Sweet Corn Soup

A very yummy soup from Alice Waters' The Art of Simple Food.

Melt in a heavy-bottomed pot over medium heat:
4 tablespoons (1/2 stick) butter
Add:
1 onion, diced
Cook until soft, without browning, about 15 minutes. Season with:
salt
Meanwhile, shuck:
5 ears of corn
Cut kernels from the cobs. Add the kernels to the cooked onions and cook for 2 to 3 minutes. Cover with:
1 quart water
Bring to a boil. Immediately lower the heat to a simmer and cook until the corn is just done, about 5 minutes. Remove from the heat and purée in small batches in a blender. (Be careful when blending hot soup in a jug blender and always make sure there is an air vent to allow the steam to escape.) Strain the soup through a medium-mesh strainer to remove any tough skins. Taste and adjust for salt as needed.

Makes 1 1/2 quarts; 4 servings

Variations:

• Garnish with creme fraîche seasoned with chopped savory, salt and pepper.
• Garnish with chopped nasturtium petals or nasturtium butter (chopped nasturtium petals worked into soft butter seasoned with salt and pepper)
• Garnish with a purée of roasted sweet or chile pepper enriched with butter or creme