First, in a slow cooker, place the chicken breasts with 1/2 cup water. Sprinkle allspice, garlic powder, salt and pepper. Cook on high setting for 3 hours.
At three hour mark, using a strainer, remove the chicken discharge but, keep the juices.
Next, in a small saucepan on med/high heat, add brown sugar, balsamic vinegar, corn starch, soy sauce and 1/2 cup of water. Stir it and cook it for about 4 minutes until it thickens. Pour onto chicken and cook the chicken for one more hour.
Storage:Store leftovers in the refrigerator for up to 5 days.Cook this recipe on low for 6 hours and add the brown sugar balsamic sauce at the 5 hour mark.