Place butter, sugar and honey in a saucepan and heat over a low heat until they melt completely, then leave to cool.
In the meantime, separately, sift into a bowl and then mix flour, cocoa, ginger and bicarbonate.
Incorporate the egg yolk and the butter mix and work quickly until you obtain a homogeneous dough, then wrap it with cling film and leave to rest in the fridge for at least 1-2 hours, or better yet overnight.
Once the resting time has passed, take the dough again, roll it out on a lightly floured work surface into a fairly thin sheet (about 0.5 cm) and cut out the little men with a cutter.
Place them on the baking tray lined with baking paper, well separated from each other, and cook them for about 10 minutes or until lightly golden in a fan oven preheated to 180°C, then leave to cool completely.
Start whipping the egg whites, then add the icing sugar first and then the lemon juice: it will not be necessary to whip the egg whites completely, just obtain a smooth and dense, but still fluid, icing.
Place the icing in a piping bag with a smooth and very thin nozzle and decorate your little men as you like, also using sprinkles, then leave to rest for at least 7-8 hours.
The cocoa gingerbread men are ready, all you have to do is let the icing dry and serve them.