Orange-fleshed sweet potatoes are often mistakenly sold as "yams." Although the two terms are often used interchangeably, a yam is acutally a different vegetable. True yams are native to Africa and a common Caribbean ingredient, but these are very rare in U.S. markets---despite what the sign in the supermarket says.
Cube the sweet potatoes immediately before adding to the pot to prevent them from discoloring.
Cook and refrigerate the stew up to two days before serving. Reheat over low heat.