Step 1: Prepare for Baking

1. Preheat your oven to 350°F (175°C). Line a 12-cup muffin pan with cupcake liners.
2. Chop the dark chocolate finely and melt it in a microwave-safe bowl at 50% power, stirring every 20 seconds until smooth. Set aside to cool slightly.

Pro Tip: Melting the chocolate slowly prevents it from burning.

Step 2: Mix the Dry Ingredients

1. In a medium bowl, sift together the flour, cocoa powder, baking soda, and salt. Whisk until evenly combined.

Pro Tip: Sifting removes lumps and ensures a light, fluffy cupcake texture.

Step 3: Cream Sugar and Butter

1. In a large bowl, use an electric hand mixer to cream together the sugar and butter. The mixture will resemble damp sand, not a smooth paste—this is normal.
2. Add the egg, egg yolk, and vanilla extract. Beat until the mixture looks smooth and creamy.
3. Mix in the melted chocolate, followed by the sour cream.

Common Mistake to Avoid: Overmixing at this stage can cause dense cupcakes. Mix only until just combined.

Step 4: Finish the Batter

1. Add the dry ingredients to the wet ingredients in two additions, mixing on low speed until just combined.
2. Gradually pour in the boiling water, about 1/4 cup at a time, mixing after each addition. Once all the water is incorporated, beat the batter on medium-low speed for 1 minute.

Pro Tip: Boiling water enhances the cocoa flavor and creates a moist, tender cupcake.

Step 5: Bake the Cupcakes

1. Divide the batter evenly among the prepared cupcake liners (about 1/3 cup per liner), filling each about two-thirds full.
2. Bake in the preheated oven for 17–20 minutes, or until a toothpick inserted into the center comes out clean.

Visual Cue: The cupcake tops should spring back slightly when touched.
Common Mistake to Avoid: Overbaking can make your cupcakes dry. Start checking at the 17-minute mark.

3. Let the cupcakes cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Step 6: Make the Raspberry Buttercream Frosting

1. Follow the Fresh Raspberry Buttercream Frosting recipe. Chill the frosting for at least 1 hour before piping.

Step 7: Frost and Garnish

1. Place a fresh raspberry upside down in the center of each cooled cupcake.
2. Fill a piping bag with frosting and pipe a swirl starting at the edge and working towards the center, covering the raspberry.
3. Garnish with additional fresh raspberries, dark chocolate hearts, or mint leaves, if desired.

Pro Tip: For a professional look, use a star tip when piping the frosting.