Mix all ingredients together in a large plastic bag and mix well. (Sometimes the dry mustard stays in little pieces). Add up to 6 chicken breasts. Let marinate 12 hrs. or overnight for maximum flavor. When ready to cook, discard marinade.
I sometimes double the recipe and add chopped red, yellow and orange peppers, and whole fresh mushrooms.
I grill the chicken outside and put all the veggies in a grill basket. Then I serve it over rice.