Preheat your oven to 400°F.
Peel and cube the sweet potato, then boil in a pot of salted water until tender, approximately 12-15 minutes.
While the potato boils, score the duck breast skin in a crosshatch pattern, being careful not to cut into the meat.
Season both sides of the duck with sea salt, black pepper, and garlic powder.
Place the duck skin-side down in a cold oven-safe skillet, then turn the heat to medium-low to slowly render the fat until the skin is golden and crispy.
Flip the duck breast and transfer the skillet to the oven for 5-8 minutes, or until the internal temperature reaches 135°F for medium-rare.
Drain the sweet potatoes and mash thoroughly with coconut milk, ghee, and finely chopped rosemary until smooth and creamy.
Allow the duck to rest on a cutting board for 5 minutes before slicing against the grain and serving over the sweet potato mash.