Place a large nonstick skillet over medium-high heat. Once hot, season the pork tenderloin with salt and pepper and lay it in the skillet. Sear the pork loin on all sides to seal in the juices, about 8-10 minutes total. (If using a regular skillet, add 1 tablespoon oil.)
Cover the bottom of a large 6-quart crock pot with the chopped onions, baby potatoes, and carrots. Lay the seared pork loin over the top and surround it with the remaining vegetables.
In a small bowl, whisk the minced garlic, Musselman's Apple Butter, Dijon mustard, soy sauce, and broth together. Pour the mixture over the pork and vegetables.
Cover the crock pot and turn on low for 6-8 hours, or high for 2-4 hours. Once the potatoes are tender, dinner is ready. Cut the tenderloin into thin slices and place on a platter, surrounded by vegetables. Taste the gravy, and season with salt and pepper as needed. Then pour the gravy over the pork, sprinkle with parsley, and serve.