In a large mixing bowl, combine all-purpose flour, soft unsalted butter, granulated sugar, vanilla sugar, egg, and unsweetened cocoa powder. Mix until a smooth dough forms. Wrap the dough in cling film and chill in the refrigerator for 30–60 minutes.

While the dough chills, prepare the white chocolate cream. In a saucepan, bring the heavy cream to a gentle boil, then pour over the white chocolate, stirring until smooth. Cover and chill until firm.

Preheat your oven to 160°C fan (180°C conventional). Roll out the chilled dough to 3-4mm thickness, cut out circles, and cut holes in half. Bake for 10–12 minutes until firm to the touch. Cool on a wire rack.

Melt the dark or milk chocolate, dip cookie halves, and sprinkle chopped chocolate on top. Whip the chilled white chocolate cream until fluffy.

Pipe the whipped cream around the base cookies, fill with cherry jam, and top with window cookies. Let sit briefly before serving.