Peel off the bark of the yam, slice to serve-able sizes, wash and set aside. Grind the tomatoes, fresh pepper and half cup of crayfish. Slice the onions Pour 150ml of palm oil into a cooking pot, allow to heat and bleach a little (about two minutes). Add half of the sliced onions. Pour in the ground tomatoes/peppers. Fry the ground tomatoes/pepper and onions for ten minutes, add water and transfer the sliced yams. Allow boiling then add crayfish, a seasoning cube, salt and allow to cook for the next ten minutes. Add the remaining sliced onions. Cover and allow to cook for another 5 minutes. Check if the yams are soft – use a cooking fork. Once the yams are soft, stir together. Stir till it thickens.