Start preparing the cake mixture, put the butter, cocoa, coffee and water on the fire, and leave it until combined.
Add eggs, baking soda and vanilla to yogurt.
Put the flour, sugar and salt in a large bowl, mix, then add the cocoa mixture and stir quickly until the mixture becomes homogeneous.
Finally, add the egg mixture and stir to combine.
Pour the mixture into a greased tray, put it in the oven, then take it out of the oven and leave it aside.
Prepare the sauce, put the butter, milk, cocoa and vanilla on the stove, and leave it until it melts.

Start adding sugar gradually, stir until the sauce thickens, then add walnuts.
Decorate the cake with nuts, leave it to cool, then serve