Pat the ham steak dry, melt the butter in a large skillet and brown the ham over medium-high heat for 3 minutes per side.
Transfer the ham to a plate and add the apple juice, raisins, brown sugar, vinegar and mustard to the skillet.
Simmer for 6 minutes until the raisins swell and the liquid reduces slightly.
Stir the cornstarch and cold water together, whisk it into the sauce and simmer for 1 minute until glossy.
Return the ham and heat it to 140°F, spooning only a thin layer of sauce over the meat.