Add sliced sleak to a large bowl, salt and pepper to taste. Sprinkle with cornstarch and toss to coat. Set aside until ready to use.

In a large skillet add a little oil, and heat over a medium heat. Add in green beans and allow them to cook for a couple of minutes. Add a couple tablespoons of water and cover, allow to cook for couple of minutes. Remove the green beans from the pan place in a bowl for later.

Add a little more oil to the pan, add in beef and allow it to sear cooking for a couple minutes on each side. Add in garlic, ginger, soy sauce, vinegar and sugar. Mix together and allow beed to finish cooking.

Add in beans, cook for a couple more minutes, top with sesame seeds, green onion and serve.