Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners and set it aside.
In a double boiler or microwave, melt the 3 ounces of bittersweet chocolate until smooth. Let it cool slightly before using.
In a large mixing bowl, whisk together the bread flour, granulated sugar, Dutch-processed cocoa powder, baking soda, and salt until well combined.
In another bowl, mix the eggs, vegetable oil, brewed coffee, white vinegar, and vanilla extract. Add the melted chocolate once it’s cooled.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Be careful not to overmix; a few lumps are okay.
Divide the batter evenly among the cupcake liners, filling them about 2/3 full. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool completely.
In a mixing bowl, beat the marshmallow creme until smooth. You can add a little vanilla extract for extra flavor if desired.
Once the cupcakes are cool, use a knife or a cupcake corer to remove the center of each cupcake. Fill each hole with the marshmallow filling, ensuring it’s generous.
In a saucepan, heat the heavy cream until it just begins to simmer. Remove from heat and add the finely chopped bittersweet chocolate. Stir until smooth and glossy.
Dip the tops of each filled cupcake into the ganache, allowing any excess to drip off. Alternatively, you can use a spoon to drizzle the ganache on top.
In a mixing bowl, beat the unsalted butter and powdered sugar until light and fluffy. Add a splash of vanilla extract and milk to reach your desired consistency.
Use a pastry bag fitted with a round tip to pipe the frosting onto the ganache-topped cupcakes. You can create fun swirls or just a simple dot in the center.
