Season chicken pieces with salt and pepper. Heat butter with oil in a skillet or large pan and brown chicken pieces until golden.
Combine ketchup, soy sauce, mustard, curry and chicken stock in a bowl. Pour over chicken pieces and add bay leaves. Cover pan or skillet and cook until chicken is tender. Once chicken is cooked, remove from pan and reserve.
Add cornstarch mixture to sauce and stir. Bring to a boil and continue stirring until sauce thickens. Add parsley. If sauce is too thick add water or more stock. Return chicken pieces to pan and heat before serving.