For the milk chocolate cookies, preheat the oven to about 160 °C. Mix the flour, cocoa powder, baking powder and salt in a bowl.
Break half of the chocolate into coarse pieces and melt with the butter and let cool a bit. Mix the chocolate-butter mixture together with sugar, eggs and vanilla sugar until everything is well mixed and a nice homogeneous mass is formed.
Then add the flour-cocoa powder mix on low speed. At the end, chop the other half of the chocolate into pieces and fold in the chocolate pieces. Using a teaspoon, place the dough on the baking tray lined with baking paper.
Leave plenty of space between cookies (about 4×4 per tray). Bake until cookies are flat and cracks appear on the surface (about 12 minutes on top rack – they don’t turn out as well on the bottom for me!).
Cool with baking paper on a wire rack until they peel easily from the paper.