Cut steak into 1/8" thick strips and place in a medium bowl. Add 1 T. cornstarch and toss to coat the beef with the starch. Set aside.
Wash lettuce and separate into individual leaves; set aside.
Make orange sauce:.
Combine orange juice concentrate, hoisin sauce, rice vinegar, soy sauce and 1 T cornstarch in a small bowl. Whisk together and set aside.
Heat oil in a large wok or skillet. Add red pepper flakes. Add half of the beef and stir fry until brown on all sides, about 1-2 minutes. DO NOT OVERCOOK. Remove from wok and set aside. Stir fry remaining half of beef. Return first half of beef to wok and add orange sauce, green onions and water chestnuts. Cook until sauce is thick and bubbly.
To Serve immediately:.
Place a small amount of beef mixture on a lettuce leaf. Top with garnishes of choice. Fold sides in and enjoy.
Remove from heat and allow to cool. Freeze in a large ziploc bag.
To serve: Thaw in fridge. Reheat in a skillet on low until just warmed through - DO NOT OVERCOOK or the meat will be tough. Place a small amount of mixture on a lettuce leaf, add garnishes of choice, roll up and eat!