Preheat the grill to medium heat around 350°F. Place a 10” cast iron skillet on the grill to preheat.
In a large mixing bowl, combine the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking powder, and salt.
In a separate bowl, whisk the eggs, melted unsalted butter, and vanilla extract until well combined.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Do not over mix.
Gently fold in the semi-sweet chocolate chips.
Carefully grease the preheated cast iron skillet with butter or cooking spray.
Pour the batter into the cast iron skillet and spread it evenly.
Place the skillet on the grill and close the lid. Grill for 12-15 minutes, or until the edges are set but the center is still soft.
Using heat-resistant gloves or mitts, carefully remove the skillet from the grill and let it cool for 1-2 minutes.
Dust with powdered sugar, if desired, and serve with a scoop of vanilla ice cream.