Wash and dry all produce. Cut potatoes in half lengthwise. Place in a large, tall-sided pan or large pot with enough salted water to cover by 1 inch. Bring to a boil and cook until easily pierced by a knife, about 15 minutes. Drain thoroughly and return to pot.

Pat duck dry with a paper towel. Season with salt and pepper. Place skinside down in another large pan. Cook over medium heat until skin is crisp and most of the fat has rendered, 12-14 minutes, pouring off and reserving fat as it renders. (TIP: Lower heat if skin burns.)

Pick and roughly chop enough rosemary leaves to give you 1 TBSP. Mince or grate garlic. Zest orange until you have 1 tsp zest, then remove peel from flesh. Slice flesh crosswise into rounds.

Adjust heat under pan with drained potatoes to medium-high, then pour in just enough reserved duck fat to cover bottom surface in a very thin layer. Add 2 tsp chopped rosemary. Cook, tossing, until potatoes are crisped and browned, 3-4 minutes. Toss in garlic and cook until fragrant, 1-2 minutes more. Season with salt and pepper, then remove potatoes from pan.

Combine maple syrup, 1 tsp mustard, orange zest, and remaining chopped rosemary in a small bowl (we’ll use more of the mustard later). Once skin is crisp, flip duck over in pan. Spoon maple syrup mixture over duck. Cook until mixture is thick and sticky and duck reaches desired doneness, 2-5 minutes. Remove duck from pan and set aside on a plate to rest. Pour remaining sauce in pan into a small bowl.

Place arugula, orange rounds, a drizzle of olive oil, and another 1 tsp mustard in a medium bowl and toss to combine. Season with salt and pepper. Stir another 1 tsp mustard into bowl with reserved sauce, along with any juices released by duck (you’ll have mustard left over). Slice duck crosswise, then divide duck, potatoes, and salad between plates. Drizzle sauce over duck.