Rinse the liver thoroughly under cold running water. Make sure to wash out all the blood traces. Pat dry with a paper towel. Using a sharp knife, remove all tough veins, if any. Cut crosswise into thin slices.
In a small bowl, combine olive oil with crushed garlic, mint, salt, and pepper. Mix until well incorporated. Generously brush the liver slices with this mixture and grill for 5-7 minutes on each side.