In a small bowl, whisk together the egg and water to make an egg wash. On a clean, dry surface, lay one wrapper down with a point toward you, like a diamond. Place one piece of chocolate near the top end of the wrapper. Brush a very thin layer of the egg wash on the edges of the wrapper. Fold the bottom corner of the wrapper up to create a triangle and gently press to remove all air from the middle. Press the edges to adhere the sides. Make sure the wrapper is sealed completely. Repeat with the remaining wrappers and chocolate pieces. Keep the folded chocolate wontons covered under plastic wrap or a damp paper towel to prevent them from drying.