Ive had good luck with potentially tough meat like big turkey breasts n thighs...even legs, by putting it in a good sized ziplock with some olive oil, garlic & herbs/seasoning (I love Cummin) & then give it a thorough beating with my hard rubber kitchen mallet.Let it rest for a half hour & repeat...seems to break up the fibers well, & the oil carries the seasoning into the meat.Also its pretty thin now & cooks fast without drying...if your sauteeing in a pan it does a great job
Hope its good however you do it up,
Merry Christmas lads
Franc