Whisk dry ingredients: In a medium bowl, sift or whisk together the all-purpose flour, unsweetened cocoa powder, granulated sugar, baking powder, baking soda, and fine salt until evenly combined.

Combine wet ingredients: In a separate bowl, whisk the egg with the whole milk, buttermilk (or yogurt), neutral oil, and vanilla extract until smooth.

Temper and mix: Pour the wet ingredients into the dry ingredients and stir just until combined. The batter will be thick. Stir in the hot water slowly (batter will thin) and mix until smooth and uniform. Do not overmix.

Portion: Divide the batter evenly among the prepared muffin cups — about 2/3 to 3/4 full each. This recipe yields 10–12 standard cupcakes; use 12 liners if you want smaller cupcakes.

Bake: Bake in the preheated oven 16–20 minutes, rotating the pan halfway through if needed, until a toothpick inserted into the center comes out with a few moist crumbs and the cupcakes spring back when lightly pressed.

Cool: Remove from oven and allow cupcakes to cool in the pan 5 minutes, then transfer to a wire rack to cool completely before frosting.

Kahlúa Buttercream

Beat butter: In a large mixing bowl with a hand mixer or in a stand mixer fitted with the paddle attachment, beat the softened unsalted butter on medium speed until creamy and pale, about 2–3 minutes.

Add dry flavorings: Add the sifted confectioners' sugar and unsweetened cocoa powder in two additions, mixing on low speed after each addition to avoid a powdered sugar cloud. Scrape the bowl down between additions.

Add liquids and adjust: Add the Kahlúa (3 tbs), espresso powder if using, and 1 tablespoon of heavy cream. Beat on medium speed until the sugar is incorporated. Increase speed to high and beat 1–2 minutes until light and fluffy. If the buttercream is too thick, add the remaining tablespoon of cream or 1 tsp more at a time until you reach piping consistency. Taste and add salt to balance sweetness.

Final texture check: The finished buttercream should hold peaks for piping but be soft enough to pipe through a large round or star tip. Transfer to a piping bag fitted with your chosen tip.

Assembly, Caramel Drizzle & Decoration

Prepare caramel: If using refrigerated store-bought caramel, warm it slightly in the microwave in 10–15 second bursts stirring between until pourable but not hot. If using homemade, ensure it is warm enough to drizzle (room temperature to slightly warmed).

Pipe buttercream: Once cupcakes are completely cool, pipe a swirl of Kahlúa buttercream onto each cupcake, starting from the outside edge and working inward, finishing with a small peak in the center. Use about 2–3 tablespoons of buttercream per cupcake.

Drizzle caramel: Using a spoon or a squeeze bottle, drizzle approximately 1/2 to 1 teaspoon of caramel sauce over the top of each frosted cupcake in a decorative pattern. Allow caramel to set for a minute.

Garnish: Sprinkle a pinch of flaky sea salt on each cupcake if desired. Add chocolate shavings or cocoa nibs on top and finish with an espresso bean or a mini chocolate-covered coffee bean placed in the center for visual impact.

Chill briefly (optional): For cleaner slices and slightly firmer frosting, chill the assembled cupcakes 15–20 minutes before serving. Bring to room temperature before serving if chilled.