Japanese Mum's Chicken

It just takes a bit of time. If you feel your chicken is cooked (and going to overcook) remove it before going on to reduce the liquid. Same thing, if you must use breast meat, remove it (so it doesn't dry out) and continue reducing the liquid .
Ingredients:

8 chicken drumsticks, skin on (the skin is important for flavour, and is so tasty to eat!)
1 cup water
1/2 cup balsamic vinegar
1/3 cup soy sauce
2 1/2 tablespoons sugar
1 garlic clove, peeled and bruised
1 small hot chili pepper, slit open, seeds removed

Directions:

Place all the ingredients in a saucepan over a high heat.
Bring to the boil, then reduce to a simmer for about 20 minutes.
Remove any scum that rises to the surface.
Increase the heat, turning the drumsticks frequently in the liquid, and cook until the liquid has reduced to a sticky glaze.
Arrange the chicken on a serving platter, remove the garlic clove and chili from the liquid, and spoon the glaze over.
NOTE It's a glaze rather than a sauce, so there's not a whole lot of it.