• If using marshmallow fluff, spoon dollops onto a cookie sheet or plate lined with wax paper. Place in the freezer as you make the dough.

Make the Dough

• In a large bowl, whisk together the flour, cornstarch, baking soda, baking powder and salt. Set aside.
• In a separate large bowl, beat together the butter, brown sugar and granulated sugar until combined. There should be no lumps of butter or brown sugar remaining.
• Beat the eggs and vanilla extract into the butter mixture. Turn off the mixer and scrape down the sides of the bowl a few times.
• Mix the flour mixture into the butter mixture. Start with the mixer on a low speed. The dough will be thick.
• Chop/break the graham crackers into pieces (about the same size as the chocolate chips) and measure out 1 cup of pieces. Mix the pieces and chocolate chips into the cookie dough. I do this with the electric mixer.

Assemble the Dough Balls

• Scoop out about 1½-2 tablespoons of dough.
• Flatten slightly and fold the sides, to create a shallow bowl shape.
• Place a large marshmallow or dollop of frozen marshmallow fluff in the middle of the cookie dough bowl shape. The marshmallow fluff won't be completely frozen solid - that's OK. Keep the fluff dollops in the freezer as you work so that they remain cold
• Pinch the dough up around the sides of the marshmallow/marshmallow fluff dollop. Then scoop out about another 1-2 teaspoons of dough, flatten slightly and place on top of the marshmallow so that it's fully covered.
• Then pinch the dough together so that the marshmallow/marshmallow fluff dollop is entirely covered. Roll the dough into a ball.
• As you work, place each dough ball in the freezer. The dough balls will need to freeze for 30 minutes. At this point, you can place them in a freezer bag and freeze for up to 2 months.

Bake

• When ready to bake, preheat the oven to 375℉ (190℃). Line cookie sheets with parchment paper or silicone baking mats. Lining the cookie sheets is absolutely necessary.
• Place the cookie dough balls at least 2 inches (about 5 cm) apart on the lined cookie sheets.
• Bake 1 sheet at a time in the middle of the preheated oven. The cookies will need to bake for about 11-14 minutes. When finished baking, the marshmallow may have started to ooze out of the top of the cookies. The cookie dough should look just set.
• Remove from the oven.
• Using a round cookie cutter/biscuit cutter that is larger than the cookies, place the cookie cutter around each cookie. Then gently draw a circular shape to mold the cookie back into a perfect circle. Optionally, add a square of Hershey's chocolate and a sprinkle of graham crumbs on top of each cookie. Cool the cookies on the cookie sheet until no longer warm to the touch.