To make the Thai flavoured marinade, mix all the marinade ingredients together in a bowl until well combined and pour into a zip lock bag.
Add the T-bone steaks to the zip lock bag and turn to coat in the marinade. Place in the refrigerator for about 1 hour but the longer the meat marinates the better.
To prepare the sweet potatoes, boil them in water on the stovetop or prick their skins with the tines of a fork and place them in the microwave at full power for 6 minutes to par-cook.
Tightly wrap each sweet potato in tinfoil (shiny side inside) with a knob of butter and a sprinkle of salt and place them between the burning coals of a fire or cook them in a 200°C/390°F oven for about 20 minutes or until soft. Give them a squeeze with a pair of tongs to check if they are ready.
Grill the T-bone steaks on a hot fire or griddle pan and baste the meat with the leftover marinade. Turn to cook on both sides to your preferred doneness; for a T-bone around 2 cm thick, it will take approximately 3 minutes on each side for medium-rare which is recommended.
Leave the meat to rest for half its cooking time.
Slice open the caramelised sweet potatoes and drizzle with olive oil and/or add knobs of butter, season with salt and freshly ground black pepper and generously garnish them fresh coriander leaves.
Tuck into these tangy Thai infused T-bone steaks and buttery sweet potatoes whilst hot.