Heres a great simple way to cook muntjac or any fillet. Saw it on country wise on tv.
Make sure fillet has been left out of fridge for a while to get to room temperature.
Chop up some thyme,mix with loads of black pepper. Rub olive oil over fillet and cover with thyme and pepper.
Heat up pan really hot and seal fillet all over including ends. Put in hot oven or aga for about 7 mins, then leave to stand on cutting board for same amount of time. Will be nice and pink in middle .
Perfect served over a bed of stir fried vegetables with nice glass of Zinfandel ! Simples.