Stir together the dijon mustard, soy sauce, 2 tablespoons olive oil, brown sugar, pepper, and minced garlic in a bowl. Place the pork tenderloin and prepared dijon marinade into a large zip top bag. Massage the bag to make sure the marinade covers all surface of the tenderloin. Refrigerate for at least two hours.

When ready to prepare the tenderloin, heat 1 tablespoon of olive oil in a large skillet over medium heat. Preheat the oven to 400 degrees. Remove the excess marinade from the tenderloin (scrape away as much as possible, or pan will over brown) and then when the oil in the skillet is hot (it should look wavy on the surface), add the tenderloin to the skillet. Cook the tenderloin for about five minutes on each side or until golden brown. Remove the skillet from the heat.

Transfer the browned tenderloin to a baking sheet lined with foil. Bake the tenderloin in the preheated oven for 30 minutes or until the internal temperature reaches 145 degrees.

While the tenderloin is baking, prepare the pan sauce. Add the butter to the still warm skillet (heat off) and allow it to melt. Either add ¼ cup of the marinade or 1 tablespoon each of dijon and brown sugar to the skillet. Also add 1 cup of vegetable broth. Place the skillet over medium heat and whisk the mixture until all of the browned bits on the bottom of the skillet have dissolved off. Allow the mixture to simmer, whisking occasionally, until the volume has reduced by about half (about 15-20 min). NOTE: Never re-use the raw, uncooked marinade and never marinate at room temperature.

When the tenderloin is finished, allow it to rest for 5-10 minutes before slicing. Spoon some of the pan sauce over top and slice into 12-16 pieces. Serve with more pan sauce.