Cut steak into small bite sized pieces and put in plastic bag to marinate for at least 1 hour, preferably overnight! Cut pita pockets in half so you have two. Spread mayonnaise liberally and put 1/2 cup shredded lettuce inside, set pockets aside...In very hot skillet cook meat in small batches for just a few minutes each. When finished with meat, take reserved marinade and put into the same pan. Scrape (deglaze) the pan and add the corn starch, cook over medium heat. When it starts to thicken add the meat; and then put meat into pockets.....ENJOY!!!!!