There are few tips to make the batter very crispy. (Beef, chicken or mushroom would be great)
Need a cup of potato starch.
1 cup of starch, add water to cover. Mix the ingredients and let it sit for hours. Allow the starch to be on the bottom and water to float at the top.
discard the water, add 1 egg white, a teaspoon of oil. (it would be hard as cement or mud. you need to work it to mix well)
Cut beef and season: kosher salt, ground black pepper, cooking wine and set aside
Prepare vegetables for sauce: onion, cucumber, pineapple, green and red bell peppers: sauce in pan, add 3 cups of water, add 2 teaspoon of soy sauce, 2 T apple cider vinegar, 1/4 cup of sugar, and starch water and thicken the sauce.
Optional: Napa cabbage, wood ear mushrooms, apples
add seasoned beef/mushrooms into the starch mixture and deep fry. Double fry would be best to make it crispy! Pour sauce over the crunchy fried beef and serve!