Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper and set them aside.

On the lowest speed add the flour, cinnamon, baking soda, cornstarch, salt, baking powder, and graham cracker crumbs all at once just until incorporated. The dough will start to thicken up a bit here. Stop as soon as you no longer see dry flour. Scrape the bowl again to make sure nothing is stuck at the bottom.

Scoop the dough into balls, about 2–3 tablespoons each (a large cookie scoop works great). Place them a few inches apart on the prepared baking sheets.

Bake for 10-12 minutes, or until the edges are lightly golden and the centers are just set. They’ll look slightly underdone in the middle—that’s perfect!

Let the cookies cool on the baking sheet for about 5 minutes before transferring them to a wire rack to cool completely.

Line a baking sheet with parchment paper and lightly spray it with nonstick spray to prevent sticking.

Place the marshmallows in a single layer on the prepared baking sheet.

Broil on high for 30 seconds to 1 minute, until the tops are deeply golden and toasted. Keep a close eye on them—they’ll toast quickly!

Immediately transfer the toasted marshmallows to the bowl of a stand mixer (or a large mixing bowl if using a hand mixer). Use a greased spatula to scoop them off easily.

Add the butter and beat on medium speed until smooth and the marshmallows are mostly melted into the butter.

Add the powdered sugar, marshmallow fluff, vanilla extract, and salt. Mix on medium-high speed for 2–3 minutes, or until the filling is light, fluffy, and spreadable.

If the filling feels too soft to pipe or spread, chill it in the fridge for 10–15 minutes to firm it up slightly.

Add the chopped chocolate to a heat-safe bowl and set aside.

In a small saucepan, heat the heavy cream over medium heat just until it begins to simmer. Don’t let it boil!

Pour the hot cream over the chocolate and let it sit for 2–3 minutes to soften.

Stir slowly with a spatula or whisk until the chocolate is completely melted and the mixture is smooth and glossy.

Let the ganache cool for 10 minutes before using. It should thicken slightly as it sits, making it perfect for drizzling.

Once the cookies are completely cool, flip half of them upside down—these will be the bottoms.

Using a piping bag fitted with a round or star tip, pipe a ring of toasted marshmallow filling around the edge of each bottom cookie. This will act as a barrier to hold in the ganache.

Spoon or drizzle a little ganache into the center of each cookie, inside the marshmallow ring. It should be just enough to fill the space without overflowing.

Top with another cookie, flat side down, and gently press to sandwich them together. The filling should reach the edges and the ganache will stay perfectly in the center.

Let the cookies sit for 15–20 minutes at room temperature, or chill them for about 10 minutes if you want the ganache to firm up more quickly.