Bring meat to room temperature. Heat a large cast-iron skillet over medium-high heat.
In a large, nonstick skillet, heat 2 tablespoons EVOO, 2 turns of the pan, over medium-high heat. As the oil heats up, slice the potatoes as thin as possible and combine with shallots. Arrange the shallots and potatoes in single layer in the hot skillet and season with salt and pepper. Cook 5-6 minutes, turn and season the flip-side of potatoes and cook 3-4 minutes more. Add watercress to pan, turn and toss with crispy potatoes. Sprinkle a little nutmeg over the hash, to taste.