Wash and dry all produce. Peel potatoes, then cut into 1/2-inch cubes. Mince garlic. Make shallow slits in duck skin in a crosshatch pattern. Season with salt and pepper. Add to a large pan skin-side down and place over medium heat. Cook until fat is rendered and skin is crisp, 10-15 minutes. Flip and cook to desired doneness, 2-5 minutes more.

Place potatoes in a medium pot with a large pinch of salt and enough water to cover by 1 inch. Bring to a boil and cook until easily pierced by a knife, 10-12 minutes. Drain and return to pot.

While duck and potatoes cook, place garlic and 2 TBSP butter in a small bowl and microwave on high until melted. Strip 1 tsp thyme leaves from stems; discard stems. Halve tomatoes and lemon. Halve, peel, and mince shallot until you have 1/4 cup minced shallot.

Add garlic butter and 1/3 cup milk (we sent more) to pot with potatoes. Mash with a potato masher or fork until smooth. Season with salt and pepper. (TIP: Add more milk as needed to give potatoes a creamy consistency.) Cover to keep warm.

Once duck is finished cooking, remove from pan and set aside to rest. Pour off all but 1 TBSP duck fat from pan, then return pan to medium heat. Add shallot and thyme leaves. Cook until shallot is softened, 3 minutes. Add demi-glace, cranberry jam, and 1/4 cup water, stirring to break up jam. Let simmer until syrupy, about 2 minutes. Stir in a squeeze of lemon. Season with pepper and more lemon (to taste).

Toss watercress and tomatoes with a squeeze of lemon and a large drizzle of olive oil in a medium bowl. Season with salt and pepper. Thinly slice duck crosswise. Divide potatoes and duck between plates, then drizzle with sauce. Serve with salad on the side.