In a second large bowl, whisk together the sugar, heavy cream, oil, eggs, and vanilla until smooth. Pour the wet ingredients into the dry ingredients and mix just until combined. Whisk in the boiling water until smooth. The batter will be thin — this is correct.

Preheat the air fryer to 325°F on the air fry setting for 3 minutes. Fill silicone liners or an air-fryer-safe muffin tin two-thirds full.

Air fry at 325°F for 9 to 10 minutes, until a toothpick inserted in the center comes out clean. Work in batches, leaving about ½ inch between liners. Cool completely on a wire rack.

Filling: Beat the butter with a hand mixer until smooth. Add the marshmallow creme and beat to combine. Add the powdered sugar and beat until smooth. Add 3 tablespoons of heavy cream, mix on low until combined, then beat on medium for about 2 minutes until light and fluffy. Add the remaining tablespoon of cream if it's too stiff to pipe.

Fill: Transfer the filling to a piping bag with a long narrow tip, reserving about a quarter for the swirls. Insert the tip into the center of each cooled cupcake and squeeze gently — you'll feel the cupcake swell slightly. Stop there and pull the tip straight out.

Ganache: Place the chopped chocolate in a medium heatproof bowl. Heat the cream just until it simmers, remove it from the heat immediately, and pour it over the chocolate. Let it sit 4 to 5 minutes without stirring, then whisk from the center outward until smooth and glossy.

Glaze: Dip the top of each cupcake into the ganache, twisting slightly as you lift to break the drip. Let set about 15 minutes.

Swirl: Using the reserved filling and a small round tip, pipe seven continuous loops across the top of each cupcake.

Plate, serve, and enjoy!