First, whip the chopped butter, just softened, with whips until you get an almost creamy consistency, then add sugar, egg white, salt and vanilla.
Finally, add the flour as well.
Finally divide the mixture in half and add the starch on one side and the cocoa on the other.
Put the mixture in a sac-à-poche with a star spout (I recommend you start with the clear one, if you have only one sac-à-poche) with a star spout and shape your biscuits on the baking tray lined with parchment paper.
Add the decorations you want to add before cooking (I put the candied cherries and the chocolate sprinkles) and cook for 10-12 minutes (they must be golden underneath and slightly on the sides, but much lighter above) at 190 ° C, in a preheated convection oven, then take out of the oven, let it cool completely and proceed with the other decorations (in my case: melted dark chocolate and chopped hazelnuts, simple icing sugar, melted dark chocolate and coconut).
Proceed in the same way for the cocoa mixture: shape, decorate (in my case: nutella and granulated sugar), cook, let it cool, finish decorating (in my case: melted white chocolate and pistachios, melted white chocolate and pralines / chocolate chips, simple powdered sugar).
The shortcrust biscuits whipped with egg whites are ready, let the chocolate solidify well before serving.