1 small onion
2 tablespoons unsalted butter
2 pounds fresh or frozen peas
5 cups chicken stock or low-salt broth
1 cup packed fresh mint leaves
1/2 cup heavy cream
1/2 cup plain yogurt
Salt and pepperFinely chop the onion. In a 4-quart heavy saucepan cook the onion in butter with salt, to taste, over moderately low heat, stirring occasionally until softened. Add the peas, 3 cups stock and simmer, covered, until peas are tender, 5 to 7 minutes. Stir in mint and remaining 2 cups stock and remove pan from heat. In a blender puree soup in batches until very smooth, forcing each batch through a sieve into a large bowl. Whisk in cream, yogurt and salt and pepper, to taste. If serving soup cold, chill, covered. If serving soup hot, reheat, but do not let boil.
