In a large bowl, combine the ground chicken, diced shiitake mushrooms, chopped cilantro, and sliced green onions. Add in minced garlic, reduced sodium soy sauce, toasted sesame oil, freshly grated ginger, seasoned rice wine vinegar, and freshly ground black pepper. Mix all the ingredients thoroughly until well combined.

Take a wonton wrapper and place about 1 tablespoon of the chicken filling in the center. Moisten the edges of the wrapper with water to help seal them. Carefully fold the wrapper in half over the filling, creating a triangle shape, and pinch the edges tightly. Repeat this process until all your filling is used up.

In a large cast iron skillet, heat 2 tablespoons of vegetable oil over medium heat. Place the potstickers in a single layer and cook for about 2-3 minutes, or until the bottoms turn golden brown.

Quickly add 1/4 cup of water to the skillet and cover it with a lid immediately. Let the potstickers steam for 2-4 minutes, or until the water evaporates completely.

Transfer the potstickers to a serving plate and serve hot with a dipping sauce of soy sauce mixed with rice wine vinegar and a dash of chili oil.