Because mock tender steak is fibrous, high heat (such as grilling or broiling) only makes the meat drier and harder. The optimal cooking method for this steak—and most chuck cuts, for that matter—is braising. Braising involves three steps:
Brown the meat by searing it in a hot pan.
Add a small amount of liquid to the pan and bring to a boil.
Lower the heat, cover the pan, and simmer—this will steam and poach the meat, adding moisture and creating tenderness.