1. In a heavy 3- to 4-quart saucepan, melt the butter over moderate heat. Add the onions and garlic and, stirring frequently, cook for about 5 minutes, or until they are soft and transparent but not brown. Watch carefully for any sign of burning and regulate the heat accordingly.
2. Stir in the chopped breadfruit and the chicken stock, and bring to a boil over high heat. Reduce the heat to low, cover tightly, and simmer for about 20 minutes, or until the breadfruit is tender enough to be easily mashed against the sides of the pan.
3. Pour half the mixture into the jar of an electric blender, add ½ cup of the cream, and blend at high speed until the mixture is reduced to a smooth puree.
4. With a rubber spatula, scrape the puree into a bowl or tureen. Then puree the remaining breadfruit mixture with the remaining cream.
5. To puree the soup by hand, force the breadfruit mixture through a fine sieve set over a deep bowl, pressing down hard on the vegetables with the back of a spoon. Or puree the mixture through a food mill set over a bowl. Stir the cream into the puree.
6. Season the soup with salt and pepper, and refrigerate for at least 3 hours, until thoroughly chilled. Taste for seasoning, and serve the breadfruit vichyssoise from a chilled tureen or in individual soup plates.
7. Before serving, sprinkle the soup with the chopped chives.
