Preheat the oven to 170°C (300°F). Pour 100g of flour sieved with cocoa powder and baking powder in the food processor, add a pinch of salt and creamed butter, and whisk.
Add milk and beaten egg, whisk again and pour the dough into a bowl. Add chopped hazelnuts and divide the dough into 8 gold paper muffin moulds. Bake in the oven for 20 minutes and let cool.
Whip double cream with an electric hand whisker, mix it with orange marmalade, transfer it into a pastry bag fitted with a star-shaped nozzle and spread it on the cupcakes. Sprinkle with gold powder and complete with one Ferrero Rocher per serving.