In a large (10 inch) cast iron skillet, melt the butter.
Add the brown sugar and granulated sugar and stir until dissolved.
Allow this to cool down until it is just warm.
Add eggs and vanilla.
Mix the flour, baking soda and salt with a whisk.
Stir in the flour mixture with the butter and sugar mixture. The batter will become thick.
Remove half of the cookie dough and pat of the mixture down in the skillet.
Layer pecans, Grahm crackers, Hershey's chocolate bars, and Marshmallows.
Press the rest of the cookie dough by flattening a little bit of cookie dough at a time in your hand and placing it on top of everything.
Bake for 30 minutes at 375 degrees.