Line a 9x9 inch pan with aluminum foil or parchment paper and spray with non-stick spray.

In a medium pot, melt the butter over medium-low heat. When the butter is melted, reduce the heat to low and add 5 cups of the mini marshmallows. Stir frequently until the marshmallows are melted.

Remove from the heat and stir in the vanilla extract and the remaining 1 cup of mini marshmallows. Stir to melt the marshmallows a bit (chunks of marshmallow are ok) then stir in the gluten free crispy rice cereal and the 14 crushed chocolate sandwich cookies.

When all of the cereal and cookies are coated with the melted marshmallow mixture, transfer to the prepared pan.

Let them sit in the pan to cool for a minute or two then use a spatula or your hands to press into the pan. (I find that spraying my clean hands with non-stick works best.)

While the marshmallow treats are cooling, melt the white chocolate chips in the microwave. Stir in the vegetable oil if needed. You want the melted white chocolate to be a pourable consistency.

Once the chocolate is melted, pour over the rice krispie treats and use an offset spatula to spread evenly over the entire pan. Immediately sprinkle the top of the white chocolate with the remaining 6 crushed chocolate sandwich cookies and press them into the white chocolate.

Cool completely then cut into 16-20 squares.