In a medium mixing bowl, cream butter, brown sugar, syrup, and vanilla until mixture is fluffy, about 1 minute.

In a separate bowl, combine flour, graham cracker crumbs, kosher salt, baking powder, baking soda, and ground cinnamon.

With the mixer on low, gradually add the dry ingredients to the wet ingredients until dry ingredients are thoroughly incorporated. In a slow, steady stream, add the milk. Continue to mix until the dough comes together and leave the side of the bowl.

Turn dough out onto a large sheet of plastic wrap. Flatten with the palm of your hand. Wrap the edges of the plastic wrap around the dough. Refrigerate for up to1 hour.

Preheat oven to 325 degrees.

Turn chilled dough out onto a lightly floured work surface. You may need to let the dough sit a room temperature for 5-10 minutes to make it easier to work with. Roll the dough until it is ¼ inch thick. Cut out cookies using a 3-inch round cookie cutter. Place cookies on a prepared cookie sheet.

Bake cookies 10-12 minutes. They will still be soft when you remove them from the oven. Allow cookies to cool 10-15 minutes until you can carefully transfer them to a cooling rack. Allow cookies to cool completely before beginning the next step.

Once your cookies have cooled, spoon approximately ¼ cup of marshmallow crème into the center of 12 cookies. Top marshmallow with a second cookie, then gently press down until the marshmallow just touches the edge. Place sandwiches on a cookie sheet and chill for at least 15 minutes.

In the meantime, melt the chocolate in a double boiler or in a heatproof bowl set over a small pan of boiling water. Once the chocolate has melted, remove pan from the heat and allow the chocolate to cool until it is still warm to the touch, but not longer hot. Slowly whisk in the oil.

Using two forks, gently place once sandwich cookie into the warm chocolate. Turn until thoroughly coated. Then remove cookies to a parchment paper lined cookie sheet. Let cookies stand until chocolate shell has completely hardened.