Line a 12-cup muffin pan with cupcakes liners and preheat the oven to 350 degrees.

Combine the ground graham crackers, sugar, salt and melted butter in a small bowl. Stir to combine. 

Divide the graham cracker mixture evenly in the bottom of the cupcake liners and tamp down to form a crust. Bake for 5 mins and remove to a rack to cool slightly. 

Whisk together the flour, cocoa, sugar, baking powder, baking soda and salt. Whisk in the buttermilk, egg, and canola oil. 

Slowly whisk in the boiling water and stir in the vanilla.

Divide HALF of the batter evenly in the cupcake liners over the graham  cracker crust. Place an unwrapped chocolate caramel square over the batter and evenly divide the remaining batter over the candies.

Bake for 15 minutes or until a toothpick inserted into the center comes out clean. Remove to a wire rack and cool to room temperature.

Place all ingredients, except the marshmallows, in a heatproof bowl set over a saucepan of simmering water. Be sure the water does not touch the bottom of the pan.

Beat with an electric mixer until thick and glossy, about 7-8 minutes.

Add in the marshmallows and continue to beat until marshmallows are melted, about 3 mins.

Remove from heat and beat for an additional 4-5 minutes, until cooled and thickened.

Fill a piping bag fitted with a large round tip about 2/3 full with marshmallow frosting. Pipe frosting in concentric circles on top of the cupcake, creating a peak. If you don't have a pastry bag, simply mound the frosting on top with a knife or offset spatula.

Press one marshmallow lightly in the center of the frosting. Use a kitchen torch to brown the marshmallow and the frosting until golden brown. 

Place an unwrapped chocolate caramel square into the icing and serve. (optional)