Prep ingredients: Preheat oven to 450°F. Wash potato and carrot, then slice lengthwise into 1⁄2-inch wedges. Peel and grate 1 clove garlic. Finely chop chives. Measure 3⁄4 cup water in a liquid measuring cup, add chicken broth concentrate and 11⁄2 teaspoons vinegar.

Season vegetables: On a rimmed baking sheet, toss carrots and potatoes with 1 tablespoon oil, 1⁄2 teaspoon salt, and a few grinds pepper.

Make garlic-herb paste: In a small bowl, combine garlic, 1⁄2 of the chopped chives, 1 tablespoon of the mustard, and 1 tablespoon olive oil; season to taste with salt and pepper. Pat pork tenderloin dry and season all over with salt and a few grinds pepper. Place pork on baking sheet with the vegetables and spread herb paste all over the top of the pork.

Roast pork & vegetables: Transfer pork and vegetables to the top rack of the oven and roast until pork is firm to the touch and the internal temperature registers 145oF, 20-25 minutes. Let rest before slicing, 5-10 minutes.

Make gravy: Meanwhile, in a small saucepan heat 1 tablespoon olive oil over medium. Add 1 tablespoon flour and cook until flour is golden, 1–2 minutes. Slowly whisk in chicken broth mixture; bring to a simmer. Cook, stirring occasionally, until gravy is thickened, about 5 minutes. Stir in 11⁄2 teaspoons mustard, and season to taste with salt and pepper.

Broil vegetables: Return vegetables to the top rack of the oven and broil on high until tender and charred in spots, 2–5 minutes (watch closely). Slice pork and stir any accumulated pan juices into the gravy. Serve pork with vegetables alongside and gravy for drizzling over, garnish with remaining chives.