Dissolve the tamarind paste in boiling water to make a smooth puree, adding water as needed to reach the consistency of tomato sauce. Chop the parsley leaves, reserving stems and set aside. Separate the scallion greens from the white parts. Leave the greens whole and chop the white parts. Set aside.
Mix the tamarind puree, white wine, hot pepper sauce to taste and salt to make the marinade. Tie the parsley stems and scallions greens in a bunch and add to the marinade. Pour the marinade over the chicken pieces, mix well and let marinate for at least 2 hours or overnight in the refrigerator.
Preheat oven to 325 degree F.
In a large frying pan, brown the grated onions and chopped white parts of the scallions in the butter (or margarine). Add garlic and cook for 30 seconds. Remove the bouquet garni from the chicken and discard. Add the chicken pieces to the frying pan and mix well.
Arrange the chicken pieces in a single layer in a baking pan and spoon the remaining marinade over the chicken. Bake, turning the chicken and basting from time to time to allow even browning, until the meat is tender and the sauce is nice and thick (50-60 minutes). If the sauce seems to be thickening too quickly, add a bit of chicken stock or water during the cooking, as needed.
Garnish with chopped parsley. Serve with fresh creamed corn and additional hot pepper sauce on the side.