Preheat oven to 350F. In a large mixing bowl combine flour, cocoa, sugar, baking powder, baking soda and salt using a whisk.
Then add, oil, milk, eggs, vanilla, vinegar, sourdough starter and whisk vigorously until fully combined. Stir in hot coffee.
Beat softened butter until creamy. Add cocoa powder, powdered sugar, salt, vanilla and milk, then beat until fully combined.
Allow cake to cool fully before frosting. Enjoy!