Lower the heat to medium low, pour in the rest of the water, stir in the brown sugar, and add the chicken - SKIN SIDE DOWN - and simmer, partially covered (leaving about a half inch crack to allow steam to escape) for 20 minutes. Because heat builds and accumulates during the simmering process, it's a good idea to stir the chicken and check the temp once in a while to make sure it's not getting so hot that the chicken and/or sauce are burning and sticking to the bottom of the pan.