Preheat your oven to 350°F (175°C) and grease your cake pans.
In a large mixing bowl, combine the dry ingredients: flour, sugar, cocoa powder, baking soda, and salt.
In another bowl, whisk together the buttermilk, vegetable oil, eggs, Kahlua, and vanilla extract until smooth.
Pour the wet mixture into the dry ingredients and stir until just combined. Fold in chocolate chips if using.
Divide the batter evenly between the prepared cake pans.
Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
Once cooled, frost with your favorite chocolate frosting or serve plain with whipped cream.