Marbled poundcake (one batter, two flavors)

Thanks to SKIMS for sponsoring! Shop SKIMS Men’s at https://skims.com/ragusea #skimspartner ***RECIPE*** 3 tablespoons oil 3-4 tablespoons cocoa powder 3 sticks (340g) softened butter 2 cups (400g) granulated sugar 1 cup (237mL) buttermilk 4 eggs 1-2 teaspoons instant espresso powder (very optional) 1/4 teaspoon baking soda 3 cups (420g) vanilla salt Get the oil hot (doesn't need to be super hot), stir in the cocoa powder and leave it to bloom while you mix the batter. Whip the softened butter with the sugar for several minutes until fluffy and a little lighter in color. Whip in the buttermilk until even fluffier. Mix in the eggs one or two at a time until reasonably smooth. Mix in a glug of vanilla, a tiny pinch of salt if you used salted butter and a big pinch if you didn't, the baking soda and the flour until smooth. Prepare a standard 9x5 inch / 23x13 cm loaf pan by greasing the inside and dusting it with flour. Put half of the batter into the pan. Mix the cocoa mixture and the espresso powder into the remaining batter, then put the resulting chocolate flavor in the pan. Use a knife to marble the flavors together if you want. Bake at 350ºF/180ºC (if using convection, adjust the temperature down per manufacturer's instructions) until a toothpick comes out clean — mine took almost 90 minutes.