Steps

1. Heat the oil in a large, heavy pot over medium-high heat. Add the chicken legs and sprinkle 1 tablespoon curry powder over them. When the legs are brown, turn them over and add another 1 tablespoon curry powder. Make sure the chicken is brown on all sides, then remove. (Some chicken will stick to the bottom.)
2. Keeping the heat on medium high, add the butter. While it melts, scrape up the browned bits from the bottom. Add the sliced mushrooms. Stir well to distribute the oil and butter. Reduce heat to medium and stir in the last tablespoon of curry powder. Let the mushrooms cook, covered, until they begin to release their juices (about 5 minutes). Put the chicken pieces back in the pot, stirring up the mushrooms so the chicken can nestle among the mushrooms.
3. Reduce the heat to medium low, cover the pot, and cook until the chicken is done, about 45 minutes to an hour. (The mushroom liquid will be all you need to braise the chicken.) Take out the chicken pieces and remove the mushrooms with a slotted spoon. Reduce the remaining liquid over high heat until it thickens, about 5 minutes.
4. Arrange the chicken pieces over rice, mashed potatoes, or pasta. Spoon the mushrooms and sauce over everything.