Pour hot water into a medium bowl, place a larger bowl on top, add the butter to the larger bowl, and then sprinkle the sugar and vanilla sugar over it. Wait 5 minutes for the butter to become soft.

While the butter softens, sift the flour with cocoa, then add the baking powder and salt. You can sift it several times; this will make the dough fluffier.

Cream the soft butter with sugar. Add the eggs and beat with a mixer. The fewer lumps that remain, the better.

Now is the perfect time to set the oven to preheat to 190 °C.

Add the flour mixture gradually. It’s best to stir with a whisk. When the dough becomes difficult to stir, add a little milk and keep mixing.

At the very end, add the chocolate, cut into small pieces. To prevent the chocolate from sinking to the bottom, stir the mixture before placing it into the pan.

We pour the batter into the molds. We personally used paper liners placed into silicone molds. Then sprinkle the tops with sugar mixed with cinnamon, although that's optional.

Put the muffins in the oven for 20 minutes. The key is to take them out immediately after the 20 minutes, otherwise they’ll over‑dry and won’t be very soft.