Preheat the oven to 350 F
In a large bowl, whisk together the egg, sugar, oil, and vanilla until smooth.
Add in the almond flour, oat flour, baking soda, and salt and stir together to form the dough.
Fold in the chocolate chips and and half of the marshmallow pieces.
Grease a 9u0022 skillet with cooking spray and flatten the dough into the skillet.
Press the remaining marshmallow bits into the top of the dough along with some extra chocolate chips.
Bake for about 15-18 minutes. I prefer 15 minutes for a gooey center.
Serve warm or cooled, slice and enjoy!
Keep leftovers stored in an airtight container for up to 1 week.