1. Season the meat by rubbing it with mustard powder and thyme. Place in a glass dish and add the 1/2 cup of sherry, 1/2 cup of soy sauce as well as the garlic and the ginger. Make sure to lather the loin good. Cover the dish and refrigerate overnight.
2. Preheat the oven to 325 degrees.
3. Bake at 325 degrees for approximately 25 minutes per pound a saucepan over medium heat. Next add the 2 tablespoons of sherry and the tablespoon of soy sauce. Stir well, reducing the heat to low and letting simmer.Pour over tenderloin as the last touch.