In a large bowl (or in your stand mixer, if you have one) whisk together eggs, buttermilk, yogurt, oil, and vanilla; add sugar, then gradually mix in flour, cocoa, baking powder, and baking soda.
300 g sugar, 7 g baking powder, 7 g baking soda, 2 eggs at room temperature, 185 g buttermilk, 185 g Greek yogurt, 100 g peanut or sunflower oil, 1 teaspoon vanilla extract, 85 g unsweetened cocoa