Mix the flour and baking soda in a small bowl and set aside.
Add the brown sugar, melted butter, vanilla extract, and salt to the bowl of a stand mixer. Briefly mix to incorporate, then add the egg and beat until smooth.
Add half the flour mixture and mix until just combined, then add the rest of the flour and mix until smooth.
Add the rolled oats and mix until a sticky dough forms.
Add the chopped chocolate and gently mix with a spoon until incorporated into the dough.
Store the dough in an airtight container in your cooler until you’re ready to bake.
At the campsite, line a cast iron skillet with parchment paper. Add the dough and spread it into an even layer.
Cover with foil, and then place over low indirect heat on your campfire or grill. Bake for about 30 minutes until the edges start to brown and the middle starts to set.
Remove from the fire, then lift the cookie out of the skillet using the edges of the parchment paper and let it cool.
Cut into a few pieces and enjoy with a dollop of whipped cream!