Special equipment: a culinary blowtorch
For the marshmallow topping: Combine the cornstarch and powdered sugar in a bowl and evenly distribute over a sheet pan. This is what you will place the marshmallows on as they finish so they don't stick.
Sprinkle the gelatin over 1/3 cup very cold water in the bowl of an electric mixer fitted with a whisk attachment.
In a small saucepan fitted with a candy thermometer, mix the granulated sugar and corn syrup with 1/3 cup water. Place over medium-high heat and bring to a simmer. When the syrup reaches 245 degrees F, remove from the heat. Turn the mixer to medium (the bloomed gelatin will be thick and clumpy--don't worry, it's supposed to look like that) and slowly pour the hot syrup into the gelatin, being careful not to hit the whisk or let it run down the sides of the bowl. Once all of the syrup is incorporated, turn the mixer to high and beat until the mixture begins to cool; it will gain volume, turn white and start to pull from the sides of the bowl, and the exterior of the bowl will be close to room temperature, 12 to 15 minutes. Add the orange extract and mix to combine.
Lightly spray a large serving spoon with cooking spray. Drop about 1/2-cup-size scoops of the marshmallow on the powdered sugar mixture and let cool, spraying the spoon in between scoops--you want 18 scoops total. Set aside.
For the cupcakes: Preheat the oven to 350 degrees F and line cupcake pans with 18 cupcake liners.
Combine the flour, granulated sugar, cocoa powder, baking soda, baking powder and salt in a large bowl. Combine the buttermilk, coffee, coconut oil, vanilla and eggs in another bowl with a whisk. Make a well in the dry ingredients and add the wet mixture, whisking until just combined.
Fill each cupcake liner two-thirds full with the batter. Bake until puffed and an inserted cake tester comes out clean, 10 to 12 minutes. Cool for 5 minutes before removing the cupcakes from the pan.
Place the marshmallow scoops on top of the warm cupcakes. Using a culinary torch, torch each marshmallow to caramelize. Serve.