In a pan, boil the water with sugar for 8 minutes, until it becomes syrupy.
Add the cacao powder, mix well and continue boiling at low temperature for another 4 minutes. Stir occasionally, so it does not crystalise or stick to the pan.
Remove the pan from the hob, add the powdered milk and mix well. Depending on the type of powdered milk used, you might want to grind it before if it is too lumpy.
During this step, you will observe that the powdered milk will quickly absorb the syrupy composition and thicken. Keep mixing until all lumps dissolve.
Add the butter and mix well. Optionally, add roasted crushed hazelnuts.
Add whatever flavours you wish. Try with small quantities first to see if you want to go for it. My favourite flavours are rum essence with a little dash of ground pepper or orange essence with pepper. The choice is yours!
At this point, the composition should be malleable enough to pour in silicone moulds if you decided to go for special occasion shapes. Larger moulds work better than smaller; the Christmas shapes I tried were not quite successful because of this!
If you are going for simple bar shapes, place a parchment paper on a tray, empty the content from the pan and level nicely with a spatula.
Cool in the fridge for at least 4-6 hours, depending on the layer's thickness. Overnight is better!
If you used shapes, carefully remove your chocolate from the silicone moulds. Otherwise, cut bars of desired thickness and enjoy when you are craving something sweet!