In a separate medium bowl, whisk together egg and sugar until well combined. Add milk, oil (or melted butter), and vanilla extract. Pour the wet ingredients into the dry ingredients and stir just until combined and moistened. Do not over mix. Mix in chocolate chips or chunks. Set aside for 15 minutes.
Chocolate sauce: In a medium heatproof bowl, combine chocolate and heavy cream. Microwave in 20- to 30-second increments, mixing in between until chocolate is melted and mixture is smooth. Set aside while making the pancakes. I like to pour it over the pancakes while it’s warm.
Heat a griddle or skillet over medium heat. Coat with cooking spray or oil. For each pancake, drop 1/4 cup of batter onto skillet. Cook 1-2 minutes, until surface of pancakes have some bubbles and the bottom appears to be done. Flip carefully and cook another 1-2 minutes. Transfer to a plate and cover loosely with aluminum foil to keep warm. Make sure to coat the skillet with oil before every pancake or batch of pancakes to prevent sticking.
Serve immediately with chocolate sauce (rewarm sauce in the microwave for a few seconds if needed).