Mocha cake

Ingredients • 250 g flour
• 100 g potato starch
• 160 g butter
• 150 g sugar
• 3 eggs
• a pinch of salt
• 75 ml milk
• 1 cup of ristretto coffee
• 1 packet of yeast
• 50 g unsweetened cocoa 
   Mix the butter with sugar until mixture is frothy.
Add one egg at a time, salt, milk and coffee.
Sift flour mixed with potato starch and yeast. Stir gently.
Pour a portion of the dough (2 | 3) into a mold, add to that remained the cocoa and a couple of spoons of milk.
Pour the dough on the cocoa and coffee, with a fork, make concentric movements in order to obtain the variegation.
Bake at 180 for 45 minutes.