How to Make It
Whisk together vinegar, garlic, 3 tablespoons of the oil, 2 teaspoons of the maple syrup, 2 teaspoons of the mustard, 3/4 teaspoon of the salt, and 1/4 teaspoon of the pepper in a large bowl until combined. Stir in farro; let stand 5 to 10 minutes.
Meanwhile, heat remaining 2 tablespoons oil in a large skillet over medium-high. Flatten pork pieces slightly using the palm of your hand. Sprinkle evenly with remaining 3/4 teaspoon salt and 1/4 teaspoon pepper. Working in 2 batches, if needed, add pork to skillet. Cook until browned on both sides and just cooked through, about 2 minutes per side. Transfer to a plate; cover to keep warm.
Add wine to skillet; stir (using a wooden spoon) over medium-high to release any browned bits from bottom of pan. Cook, stirring often, until wine reduces by half, 1 to 2 minutes. Whisk in remaining 2 teaspoons maple syrup and 1 teaspoon mustard. Remove from heat. Add butter, stirring until butter melts, about 1 minute.
Add arugula and apple to farro mixture in bowl, and toss to coat. Divide salad and pork evenly among 4 plates, and spoon sauce over pork.