If you're looking to add more iron and Vitamin B to your diet, try eating more beef liver. While beef liver can be quite tough, calf liver will be more tender than that from an older cow. However, if you can't find calf liver or you want to tenderize the beef liver even further, try soaking it in milk for at least two hours before you cook it.
Place your beef liver in a bowl. Make sure you choose a bowl that is large enough for the liver to lay flat and high enough for the milk to completely cover it.
Pour milk into the bowl over top of the beef liver. Continue pouring until you have completely covered the liver. It doesn't matter what type of milk you use.
Cover the bowl with plastic wrap and place it in your fridge.
Remove the bowl from the fridge after at least two hours. If you know your beef liver is particularly tough, leave it in the fridge for another hour.
Remove the plastic wrap from around the bowl. Remove the beef liver and rinse it in lukewarm water.
Pat the beef liver dry with a cloth and prepare it for cooking.