Preheat the oven at 170ºC/340ºF conventional oven and line 2x 15 cm/6 inch baking pans with parchment paper.
Start by making the coffee and weigh it out so it can cool down a bit while preparing the other ingredients.
120 g warm coffee or water
In a bowl, sift all of the dry ingredients together. Give it a stir to make sure everything has been combined.
120 g all-purpose flour, 2 teaspoon cornstarch, 100 g granulated sugar, 50 g brown sugar, 25 g unsweetened cocoa powder, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
In another mixing bowl add all of the wet ingredients, including coffee, and with a hand whisk, whisk them together until combined. Be sure to not mix the ingredients too vigorously so the eggs don’t get over mixed.
55 g vegetable oil, 90 g sour cream 14-18%, 1 large eggs, 1 teaspoon vanilla extract
Slowly pour the wet ingredients into the dry while gently stirring it all together. Make sure there are no lumps left in the batter.
Divide the cake batter into the two prepared baking tins and bake them for 22-24 minutes or until a cake tester comes out clean.
Let the cakes cool on a cooling rack. After 5 minutes, gently remove the cakes from the cake tins and let the cakes cool down completely.