Combine Mustard, Worcestershire, Salt, Pepper And Thyme. Rub This Mixture Over The Chicken And Let Sit For 1 Hour. Heat Oil In Skillet And Brown Chicken Well. Remove And Set Aside. Fry Onions In The Same Oil Until Translucent About 5 Minutes. Return Chicken To Skillet, Add Water And Cover The Pan. Simmer Over Moderate Heat For 30 Minutes. Serve Warm With Tortillas.