For the chocolate sticks, cut the cold butter into cubes and stir with the powdered sugar until smooth, add the egg yolks and stir with the cocoa until the mixture is smooth, then stir in the flour.
The dough should be ready to be piped. Using a piping bag and a smaller nozzle, pipe 4-5 cm long strips onto a baking tray lined with baking paper and bake for 8-10 minutes at 170 °C convection oven.
When cooled, fill with jam, dip one side in the glaze and then let the chocolate sticks dry.