Chocolate Cupcakes

I adapted this recipe from America's Test Kitchen Ultimate Chocolate Cupcakes with Ganache Filling.

I made these for my sister's 23rd birthday. I frosted them the day before and put them, covered, in the refrigerator. They will stay good for the next couple of days. Just be sure to give them about 30 minutes at room temperature to warm up.

Ganache Filling
2 ounces bittersweet chocolate , chopped fine
1/4 cup heavy cream

Chocolate Cupcakes
3 ounces bittersweet chocolate , chopped fine
1/3 cup (1 ounce) Dutch-processed cocoa
3/4 cup hot coffee
3/4 cup (4 ounces) bread flour
3/4 cup sugar
1/2 teaspoon sea salt
1/2 teaspoon baking soda
6 tablespoons olive oil
2 large eggs
2 teaspoons white vinegar 

FOR GANACHE FILLING:

Heat the heavy cream in the microwave until hot. Add the chocolate and stir until smooth and shiny. Refrigerate for 30 minutes (no longer than that).

FOR CUPCAKES:

Line standard-size muffin pan (cups have ½-cup capacity) with liners.

Place chocolate and cocoa in a large bowl. Pour hot coffee over mixture and whisk until smooth. Set in refrigerator to cool completely, about 20 minutes.

Whisk flour, sugar, salt, and baking soda together in medium bowl; set aside. To the chocolate-cocoa mixture, add oil, eggs and vinegar. Add flour mixture and whisk until smooth.

Transfer the batter to a 4 cup measuring cup (or larger) and fill the muffin liners about 3/4 way full. Divide the ganache between the cupcakes (place a blob right in the middle).

Bake at 350 F (middle of the oven) until cupcakes are set and just firm to touch, about 20 minutes. When cupcakes are cool enough to remove, lift each cupcake and set on wire rack. Cool to room temperature before frosting.

TO FROST:

Place a blob of frosting on center of each cupcake. Using small icing spatula or butter knife, spread frosting to edge of cupcake, leaving mound in center.

Chocolate Frosting
1/3 cup sugar
2 large egg whites
Pinch sea salt
12 tablespoons (1 1/2 sticks) unsalted butter , softened and cut into 1-tablespoon pieces
6 ounces bittersweet chocolate , melted and cooled

For malted chocolate frosting: use 1/4 cup sugar and add 1/4 cup malted milk powder along with the melted chocolate in step 5.

1. Combine sugar, egg whites, and salt in bowl of stand mixer; place bowl over pan of simmering water.

2. Whisking constantly until the mixture is 160 F on instant-read thermometer, 2 to 3 minutes.

3. Place bowl in stand mixer fitted with whisk attachment. Beat mixture on medium speed until consistency of shaving cream and slightly cooled, 1 to 2 minutes.

4. Add butter, 1 piece at a time, until smooth and creamy. (Frosting may look curdled after half of butter has been added; it will smooth with additional butter.)

5. Once all butter is added, add cooled melted chocolate and vanilla; mix until combined. Scrape the sides of the bowl and beaters. Increase speed to medium-high and beat until light, fluffy, and thoroughly combined.