Preheat oven to 375°F or 190ºC.

Melt the chocolate, the caramel and the butter in a bain-marie. Mix well. Keep warm.

In the meantime, pour the flour, cocoa, coffee, and salt in a big bowl and mix well. Set aside.

Mix the eggs and sugar at high speed with an electric mixer for about 2-3 minutes, until you get a light and foamy texture.

Pour the chocolate mixture into the egg mixture and mix at medium speed until homogenous. Then, add the flour mixture, the beer and nuts and continue to mix until homogenous.

Cover a 9x13 edged baking pan with parchment paper. Pour in the mixture and sprinkle it with chocolate chips. Add Fleur de sel to your liking.

Oven bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.

Let it cool completely. Cut and enjoy!