Prepare the caramel and coat a 9-inch round cake pan, reserving the extra caramel sauce in the refrigerator as directed above. Preheat oven to 400 degrees. Rub the yam with vegetable oil, place on a baking tray and bake 45 minutes to 1 hour, until a knife easily pierces the potato at its thickest part. Set aside until cool enough to handle, then peel and mash with a fork (the mashed potato should measure about 1 cup). Reduce the oven temperature to 325 degrees. Prepare the caramel and coat a 9-inch round cake pan, reserving the extra sauce in the refrigerator as directed. In a large bowl combine all remaining ingredients. Mix thoroughly. Pass through a strainer, pressing with a spatula, into the caramel coated cake pan. Place the cake in~ a water bath. Bake for about 1 hour and 10 minutes or until the center just feels firm when pressed. Set aside to cool in the water bath. Remove from the water bath, cover with plastic wrap and refrigerate 4 to 6 hours, or overnight. To serve cut in wedges and top with cold caramel sauce.