A pan sauce is a deceptively simple way to make even a quick weeknight meal feel special. Use a liquid like broth and/or wine to pull up the browned bits in the skillet left over from searing your protein-in this case, pork loin (those bits are called the "fond"), and you're most of the way there. The fond is loaded with flavor, so it doesn't take much more to make a really beautiful sauce happen.
In a small bowl, whisk together the broth, mustard, Pluck, and maple syrup. In a small cup, dissolve the arrowroot in 1/2 teaspoon of water.
Warm the avocado oil in a large skillet over high heat. Season the pork all over moderately with salt and pepper. Place the pork slices in the skillet and cook until seared on both sides, turning once, 2 to 3 minutes total. Transfer the pork to a plate; tent with foil to keep warm. (Work in batches if needed to avoid crowding; add more oil to the skillet between batches.)
Lower the heat to medium. If there is less than 1 tablespoon of fat in the skillet, add more oil to equal about 1 tablespoon. Add the shallot to the pan, sprinkle lightly with salt, and cook, stirring, until tender and turning golden, 2 to 3 minutes. Whisk the broth mixture and pour it into the skillet, stirring to pull any browned bits from the bottom. Lower the heat to medium-low, add the rosemary, and simmer until the mixture has reduced by about one-third, 3 to 4 minutes.
Stir the arrowroot mixture, then pour it into the skillet and stir to combine. Add the pork slices along with any juices that have collected on the plate. Cook until the pork is warmed through and the sauce has thickened 2 to 3 minutes longer, turning the pork once or twice to coat it with sauce. Serve hot, topped with spoonfuls of the sauce and a sprinkling of parsley and more Pluck, if desired.