Butter and flour a loaf pan or 23 cm round bundt pan.
Preheat oven to 160˚ C fan.
Mix cocoa powder and coffee in a small bowl.
Mix flour, baking powder, baking soda, salt and sugar in another bowl.
In a mixer bowl add melted butter, olive oil, eggs, vanilla, yogurt and the cocoa-coffee mixture. Beat to combine. Add the flour-sugar mixture and beat on slow speed until almost combined. Continue mixing with a spatula until just combined. Don’t overmix.
Transfer mixture in cake pan. Bake for 30-35 minutes. The cake will rise but may sink in the middle slightly.
Make the syrup while cake bakes. Mix water, sugar and cocoa powder in a small saucepan. Bring to a boil and remove from heat. Add cognac if using.
As soon as cake comes out of the oven, brush the surface with syrup. Invert cake on a platter and brush the remaining syrup all-over. Let cake stand until cool. Slice and serve.