Begin by dissolving 2 tablespoons of instant coffee in 1/4 cup of hot water, stirring until fully combined. Allow the mixture to cool to room temperature.

In a mixing bowl, whisk together 3 large eggs and 1/2 cup of castor sugar until smooth and pale, about 3-5 minutes. Gradually incorporate the cooled coffee mixture.

Sift in 1 cup of cake flour, 1/4 cup of cocoa powder, 1 teaspoon of baking powder, and a pinch of salt. Gently fold until just combined.

Melt 1/2 cup of unsalted butter and stir it into the batter until fully incorporated.

Cover the bowl with plastic wrap and refrigerate for 1-2 hours.

Preheat the oven to 370°F (190°C) and lightly grease the madeleine pan.

Transfer the batter into a piping bag or use a spoon to fill each mold in the madeleine pan about 80-90% full.

Bake the filled madeleine pan for 10-12 minutes until puffed and golden brown.

Transfer the madeleines to a wire rack to cool completely.

In a mixing bowl, beat together 1 cup of mascarpone cheese, 1/4 cup of confectioners’ sugar, and 1/4 cup of heavy whipping cream until fluffy. Optionally, mix in 1 tablespoon of Kahlua.

Create holes in the cooled madeleines and fill them with the mascarpone mixture, finishing with cocoa powder dusting.