Step 1: In a large bowl, cream together the softened butter, granulated sugar, and brown sugar with an electric mixer until light and fluffy.
Step 2: Beat in the creamy peanut butter until well combined, then add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Step 3: In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined. Do not overmix.
Step 4: Drop rounded tablespoons of dough onto baking sheets lined with parchment paper. Use a fork to create a crisscross pattern on top of each cookie.
Step 5: Bake in a preheated oven at 375°F (190°C) for 8-10 minutes, or until the edges are lightly golden and the centers are still slightly soft. They will set as they cool. Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Step 6: Once the cookies are completely cool, spread a generous spoonful of marshmallow fluff onto the flat side of half of the cookies. Top with the remaining cookies to create sandwiches.
Step 7: In a microwave-safe bowl, combine the semi-sweet chocolate chips and coconut oil. Microwave in 30-second intervals, stirring after each, until smooth and melted.
Step 8: Dip half of each sandwich cookie into the melted chocolate, allowing any excess to drip off. Immediately sprinkle the melted chocolate with crushed graham crackers.
Step 9: Place the finished cookies on a parchment-lined tray and refrigerate for 15-20 minutes, or until the chocolate has set. Enjoy!