In a large bowl, whisk together the flour, cocoa powder, baking powder, and salt.

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

Preheat the oven to 350°F. Line a muffin tin with paper liners and fill each two-thirds full.

Bake 18 to 20 minutes, until a toothpick in the center comes out clean. Cool 5 minutes in the pan, then completely on a wire rack.

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 9 to 10 minutes, until a toothpick 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 cream, mix on low, then beat on medium about 2 minutes until fluffy. Add another 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 until you feel it swell slightly.

Ganache: Place the chopped chocolate in a heatproof bowl. Heat the cream just until it simmers, pour it over the chocolate, and let sit 4 to 5 minutes without stirring. Whisk from the center outward until smooth and glossy.

Glaze: Dip the top of each cupcake into the ganache, twisting slightly as you lift. 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.