Place butter in a large microwave proof bowl. Heat butter for about 15 seconds, until melted fully. Let sit for a few minutes to cool slightly.
Add in sugar and peanut butter into bowl. Whisk until combined.
Add in eggs and vanilla extract and whisk.
In a separate medium bowl, whisk all dry ingredients (flour, cinnamon, baking soda, baking powder, salt).
Pour dry ingredients into wet ingredients. Mix well with a spatula. Pour in chocolate chips and mix.
Butter a 9’’ cast iron skillet. Pour into cast iron skillet.
Sprinkle top with chocolate chips, marshmallows and Golden Grahams. If you want them to be more uniform, combine all 3 in a small bowl and then pour over.
Bake for 25-30 minutes- set around edges, slightly gooey in middle. Let cool slightly before serving.