Preheat the oven to 180°C. Grease 2 x 12 bun madeleine trays.
In a large mixing bowl, cream the butter and sugar using an electric hand held whisk until pale and fluffy. Beat in the eggs one at a time, mixing well between additions. Sift together the flour, cocoa powder, baking powder and salt in a separate mixing bowl.
Stir into the butter, egg and sugar mixture until incorporated. Fold in the apple. Fill the madeleine tins with the batter and bake for 10-12 minutes, until the madeleines are springy to the touch.
Remove and cool the tins on a wire rack for 15 minutes. When cool, remove from the tins and arrange in tea cups to serve.