Cream the butter and sugar together with an electric hand mixer or stand mixer until fluffy and light in color. Add the eggs and vanilla and continue to beat.
In a separate bowl, combine the Graham cracker crumbs, flour, baking soda, baking powder and salt. Slowly add the dry ingredients to the wet ingredients and mix into a soft dough. Chill the dough for 30 minutes in the refrigerator.
Bake the cookies at 350°F for 10 to 12 minutes, until lightly browned on top. Let the cookies cool on the baking sheet for 2 minutes and then press a piece of the Hershey’s chocolate bar into the center of each cookie. The chocolate will melt a little into the cookie; if it is melting too much, wait another minute. Transfer the cookies to a cooling rack and cool to room temperature. When ready to glaze, place the cooling rack over a baking sheet.
Heat a large sauté pan over medium-high heat. Add the mini marshmallows and butter to the pan. When they start to melt, stir constantly until the marshmallows and butter have melted and are combined and the mixture is smooth. To toast the marshmallow cream, let the melted marshmallows sit in the pan for 20 seconds without stirring. Then turn off the heat and gently run a spatula through the marshmallow cream to swirl the toasted marshmallow on the bottom of the pan into the rest of the cream. Do not over stir, you just want to swirl the toasted marshmallow into the cream not combine it.
Using a spoon, immediately drizzle the cookies with the melted marshmallow cream. If the marshmallow cream starts to set up, place it back over the heat for a few seconds to warm it up again, try not to stir it.
Let the chocolate and marshmallow drizzle set up before serving or storing. Store the cookies in an airtight container with parchment paper in between the layers, so the cookies don’t stick together. They are S’mores cookies…so they are gooey!