Preheat oven to 300°F.
Rub bottom round with dry rub.
Preheat Dutch oven on medium heat, add ghee and sear roast on all sides, for 2-3 minutes per side.
Add ginger, lemongrass, Thai chilies, onion and garlic. Sauté until onions are golden.
Add mirin and coconut milk scrapping the bits off of the bottom of the Dutch oven.
Remove from heat, cover and place in oven for 4-5 hours or until meat is fork-tender.