Preparation Steps

• Make the ganache first: Place chopped chocolate in a heatproof bowl. Warm the cream in a small saucepan over medium heat just until steaming (do not boil). Pour over the chocolate, cover the bowl, and let stand 2–3 minutes. Stir slowly from the center outward until glossy and smooth. Set aside at room temperature to thicken while you bake.
• Position a rack in the center of the oven and preheat to 340°F (170°C). Line a muffin pan with 16 paper liners (you may need two pans).
• Bloom the cocoa: In a bowl or large measuring cup, whisk the hot coffee, cocoa powder, and espresso powder (if using) until smooth and shiny. Let cool until warm, about 5 minutes.
• Whisk the wet ingredients: In a separate medium bowl, whisk together sugar, eggs, egg yolk, sour cream, oil, vanilla, and honey until glossy and well combined.
• Combine: Whisk the cocoa-coffee mixture into the egg mixture. In a large bowl, whisk flour, baking powder, baking soda, and salt. Pour the wet mixture into the dry and whisk gently just until no dry streaks remain; the batter will be fairly thin.
• Fill and bake: Divide batter among liners, filling each about two-thirds full. Tap the pan once to release any large air bubbles. Bake 17–19 minutes, rotating the pan halfway, until the tops spring back and a toothpick comes out with a few moist crumbs. Cool 5 minutes in the pan, then transfer to a wire rack to cool completely.
• Adjust ganache consistency while cupcakes cool: If it’s still loose, refrigerate 5–10 minutes until it holds a soft mound. If too firm, warm briefly (5–10 seconds) and stir until spreadable.
• Core and fill: Use a small paring knife or the wide end of a 1/2-inch piping tip to remove a plug from the center of each cupcake. Pipe or spoon about 2 teaspoons of ganache into each cavity, then place the plug back on top, trimming if needed to sit flush.
• Make the frosting: Melt the chocolate in short 20–30 second bursts at 50% power, stirring until smooth; cool until barely warm. In a stand mixer fitted with the paddle, beat butter on medium-high until very pale and creamy, 3 minutes. Sift powdered sugar and cocoa together. Mix in half on low speed, then add vanilla and 2 tablespoons cream and beat 30 seconds. Add remaining sugar/cocoa and beat 1 minute. Scrape the bowl, stream in the cooled melted chocolate on low, then increase to medium-high and whip 2–3 minutes, adding more cream a tablespoon at a time until fluffy and pipeable. Mix on low for 30 seconds to smooth.
• Finish: Transfer frosting to a piping bag fitted with a large open star tip and swirl generously over each cupcake. Drizzle with any leftover ganache or finish with a pinch of flaky sea salt.