In a separate large bowl, add the melted butter, oil, both sugars, and mix with a nonstick spatula to combine. Add in the egg and egg yolk then mix again until completely homogenous. Add in the dry ingredients and the chopped chocolate and mix until a thick dough forms.

Line a cookie sheet with parchment paper. Use a 3-4 tablespoon cookie scoop (these are big cookies) to scoop the dough.

After scooping, before releasing the dough onto the sheet, make a divot in the dough while it's still in the scoop. Spoon or pipe a tablespoon of marshmallow fluff into the divot.

For a smooth cookie with the fluff completely encased, add another piece of cookie dough over the fluff center, then place the cookie on the tray.

For exposed fluff, like in the photos above, make sure only a small bit of fluff pokes through, with the dough encasing the rest. Place the cookie fluff side up on the parchment paper, and continue with the rest of the dough.

Chill cookies on tray for at least 1 hour, or up to 24 hours.

Bake at 350F for 10-12 minutes then remove from oven and use a circular cookie cutter to create the perfect shape. Top with additional graham cracker crumbs and let cool.