In the sealable plastic bag add the flour, brown sugar, chocolate chips, and white sugar. Seal, then put aside until needed.
To Prepare
Preheat the skillet and Dutch oven lid.
Add to the plastic bag the melted butter, milk, and egg. Mash together with your hands until the ingredients combine to form a firm dough.
Add the baking paper to the skillet. Add the dough on top and spread to evenly cover the base of the skillet.
Set the skillet at 300 degrees F (150 degrees C). This can be done by using 5 charcoal briquettes on the bottom and 10 on top.
Cook for 90 minutes, the charcoal briquettes will need to be changed halfway through as typically they only last 45 minutes.
Once cooked, let sit for 10 minutes to cool. The skillet cookie can be removed then cut into pieces, or cut and served in the skillet. If cutting in the skillet use a butter knife and be careful not to damage the seasoning on the skillet. Serve warm.