In a large, non-reactive bowl, thoroughly combine the walnut oil, ginger, molasses, onion, salt, and pepper; add the pork pieces and turn to coat evenly. Marinate, turning pork occasionally, at least 12 hours or overnight.

Preheat oven to 350ºF.

Bring pork to room temperature. Heat oil in a large cast iron skillet over medium-high heat. Add pork and sear on all sides. Transfer skillet to oven and roast pork to desired doneness, 140ºF recommended (10-15 minutes, depending on thickness). Let rest 8 minutes, slice each serving piece into 3-4 thin slices and serve at once.

As shown here, served over Sweet Potato Chorizo Hash.