The Keys to Crispy Skin
With a few important details in mind, perfectly crispy Moulard duck skin is easy to achieve.
Cast iron can store a ton of thermal energy and its surface remains completely flat at high temperatures. It's the perfect surface to sear Moulard duck breast. Just be sure to have a burner that's large enough to heat the entire surface because cast iron isn't very conductive.
Scoring the the skin allows the fat to render out. With more scoring lines (and more fat rendering), the skin becomes thinner and crispier. Place the duck breast in the freezer for a few minutes before scoring. When the skin is cold and firm, it's easier to cut many scoring lines into the duck.
Medium-high heat will do. Pay special attention to the skin as it cooks. The final coloring should be golden brown.