Preheat the oven to 350 F (180 C).
Prepare 8 muffin cups and set aside.

Melt the chocolate and mix with fleur de sel.

In the mixer bowl, combine flour, baking powder, sugar, cocoa, eggs, and softened butter.
Add the melted chocolate mixture and mix well again.

Pour the mixture into the prepared muffin cups and bake for 35 to 40 minutes.

The syrup:
Bring the water and sugar to a boil for the syrup.
After removing from the oven, brush the cupcakes with half of the syrup.
5 minutes later, brush again to make them more moist.