In a small bowl, mix mustard powder, pepper, thyme, salt together.
Rub Olive Oil over the pork tenderloins; then rub the dry seasonings mixture onto the tenderloins.
Put the olive oil, soy sauce, pickled ginger, and garlic in a large plastic baggie. Seal and mix the from the outside of the bag with your hands. Place the seasoned pork tenderloins into the marinade; seal and place into refrigerator for 2-3 hours.
Sauce
Place the heavy whipping cream, whole grain seed mustard, salt and pepper into a blender, food processor, or bullet and mix on high. It will look like whipped cream and blend to desired thickness. Place into refrigerator until ready to serve. You may serve cold with pork tenderloin or lightly heat up.
Cooking the Tenderloin
Heat grill to high or oven to 375°F. Grill or Roast about 25 minutes. Let rest lightly covered with foil for 15 minutes. Serve with Sauce.