Whisk flour, sugar, cocoa powder, baking soda, baking powder and salt. Set aside. In a large measuring jug whisk together oil, eggs, buttermilk, sour cream and vanilla until combined. Pour the wet ingredients into the dry ingredients. Dissolve the espresso powder into hot water, then add to the batter and whisk until completely combined. Set aside as you prepare the Biscoff cheesecake filling.