Chocolate Toasted Marshmallow Cupcakes

From 6 Bittersweets
Filling adapted from There Goes the Cupcake; frosting adapted from Annie's Eats
Makes 12 cupcakes

XIAOLU'S NOTES: If using homemade marshmallow fluff, the cupcakes will need to be stored in the fridge and allowed to come to room temperature just before eating.

Scant 1 cup white sugar
3/4 cup PLUS 2 Tbsp all-purpose flour
6 Tbsp unsweetened cocoa powder
1 tsp baking soda
1/2 tsp baking powder
1/2 tsp salt
1 large egg, room temperature and lightly beaten
1/2 Tbsp apple cider vinegar plus milk to equal 1/2 cup
1/4 cup vegetable oil
1 tsp pure vanilla extract
1 oz. bittersweet chocolate, finely chopped
1/2 tsp instant coffee/espresso powder
1/2 cup BOILING water

Toasted Marshmallow Filling (Recipe below)
Chocolate Sour Cream Frosting (Recipe below)
Mini marshmallows (optional garnish)

Preheat the oven to 350 degrees F. Grease top of a standard muffin pan, then line with paper liners.

In large bowl, stir together the sugar, flour, cocoa, baking soda, baking powder, and salt. Add the egg, milk, oil, and vanilla extract. Beat by hand or with an electric mixer on medium speed until well combined. Place chopped chocolate and instant coffee powder into a heatproof measuring cup and pour in boiling water. Stir or whisk until chocolate has fully melted and combined with the liquid. Pour coffee mixture into batter and mix just until combined. Don't worry if the batter seems thin; that's how it's supposed to be!

Fill cupcake liners until they are about 2/3 full (Do NOT overfill! I like to use my large cookie scoop for this.). Tap the pan firmly against the counter 2 times to remove any air bubbles. Bake for 18 to 23 minutes or just until a toothpick inserted into the middle of a cupcake comes out clean. Let cupcakes cool in the pan for 2 minutes, then remove them to a wire rack and let them cool completely there before frosting.

Transfer toasted marshmallow filling to a piping bag fitted with a long pointed tip. Insert tip into each cupcake and squeeze out a small amount of filling into the cupcake. (You'll know the cupcake is filled to capacity when its top starts to lift slightly. You should immediately stop squeezing that that point or filling will start pushing up out of the cupcake.)

Spread or pipe chocolate frosting on to cupcakes (I used Ateco #808 - a large plain round piping tip). Place a few mini marshmallows on top of each cupcake, if desired, and toast lightly with a kitchen blowtorch (be careful to avoid melting the chocolate frosting underneath). Enjoy and I hope you'll watch BBC's fantastic Sherlock show! 

Toasted Marshmallow Filling
1.5 oz. (8 or 9 large store-bought) marshmallows
1/4 cup (1 oz.) powdered sugar, sifted
5 Tbsp unsalted butter, room temperature
1/4 tsp pure vanilla extract
3 oz. (1 cup) Marshmallow Fluff (Recipe HERE or store-bought is fine)
Pinch of salt

Place the marshmallows on a cookie sheet lined with parchment paper or silicone mat. Broil on a lower rack in a toaster or conventional oven until nice and brown. DO NOT STEP AWAY from the oven; they go from brown to burned very fast! (You can also toast the marshmallows with a kitchen torch if you have and know how to safely wield one ^_^.) Let toasted marshmallows cool while you combine the butter and powdered sugar in a medium bowl. Using an electric mixer on low speed, beat until well combined. Add vanilla and mix on high for 1 minute. Add marshmallow fluff, toasted marshmallows, and salt, and mix on medium for 1 to 2 more minutes. The filling will not be completely smooth; a few chunks of toasted marshmallow are fine (and tasty!).

Chocolate Sour Cream Frosting
Makes enough to frost 12 cupcakes

4.75 oz. bittersweet chocolate, finely chopped
6 Tbsp cream cheese, room temperature
3 Tbsp unsalted butter, room temperature
1 cup powdered sugar
2 Tbsp unsweetened cocoa powder
Pinch of salt
Scant 3/4 cup sour cream

To make the frosting, melt the chocolate in a heat-proof bowl set over a pot of simmering water. Set aside to cool until just barely warm. In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese and butter on medium-high speed until pale and fluffy, about 3 to 4 minutes. Gradually mix in the confectioners’ sugar, cocoa powder and salt. Beat in the melted and cooled chocolate and then the sour cream. Continue beating until the mixture is smooth and well blended. Frost cupcakes immediately before the chocolate hardens and the frosting sets.