Preheat the oven to 350°F and position a rack in the middle.
Add the butter to the cast iron skillet and set it over medium-low heat until melted.
In the meantime, add the flaxseed meal and water to a medium bowl and mix until uniform.
Once the butter has melted, add it to the bowl with the flax egg. Use a pastry brush to spread any excess butter in the cast iron pan to grease it before baking. Set aside.
Add the sugars, vanilla, baking powder, soda, and salt to the bowl and stir to combine.
Add in the flour and mix until a smooth cookie dough forms.
Lastly, stir in all but 1 tablespoon of the chocolate chips until uniform.
Transfer the dough into the cast iron skillet and spread it out evenly. Sprinkle the remaining chocolate chips on top and press them gently into the dough.
Place into the oven to bake for 27 to 30 minutes, or until edges are golden brown and the center is set.
Remove it from the oven and allow it to cool slightly. Top it with vegan ice cream if desired, grab some spoons and dig in!
