Tried a new one the other day....It's actually alot easier than it sounds.
1 whole deer backstrap
1 red onion
1 clove garlic
1 red apple
1 lemon
1 stick butter
olive oil (smoked if available)
worcestershire sauce
brown sugar
parmesan cheese
Saw this on HUNT, FISH, COOK. Gave it a try and actually liked it pretty good. We decided to keep several whole backstraps this year just for stuff like this. Trim fat/skin off backstrap and make a horizontal cut into the side, butterflying the meat. The recipe didn't call for it, but I would recommend some meat tenderizer or lightly tenderizing with meat mallet but not too much. Don't want it too flat. Put just enough olive oil in skillet to cover bottom and set to medium heat. Depending on size of backstrap, dice about half the apple, half the onion, and whole garlic clove. Add to skillet with a few good chunks of butter and a couple of whopping doses of worcestershire. Let simmer until apple/onion are tender then add a hefty pinch or two of brown sugar. Cut lemon in half and squeeze juice into skillet also. Let simmer about another 2-3 minutes. Remove from skillet into a bowl and let cool. Add handful of parmesan to bowl and mix. Put contents of bowl into backstrap and fold together. The recipe calls for string to tie the backstrap together, but I just used toothpics. Put backstrap into skillet and cook until medium rare, flipping occasionally if needed, careful not to overcook. Remove meat from skillet, remove toothpics/string and cut into round "medallions". Pour remainder of oil in skillet over medallions. Then, yum-yum time!!! Goes great with some taters and an ice cold beer!!!

If you don't have a whole backstrap, try cooking all the stuff in a skillet and just pouring it over some deer steak.