First, bone the chicken. To bone the legs, cut down along the bone on all sides, drawing out the bone with an even movement. Cut all the chicken meat into thin strips.
Heat the oil in a wok and stir-fry the garlic, chicken and the green and red peppers.
Pour off any excess oil and deglaze the wok with the vinegar. Stir in the soy sauce, sugar and stock.
Gradually stir in the chili sauce, tasting after each addition. Season with a little salt and pepper to taste.
Cook until the sauce has reduced slightly. Serve piping hot.