Preheat oven to 350F (175C). Grease and flour a 9x13 inch baking pan.
In a large bowl, whisk together the flour, sugar, cocoa powder, baking powder, baking soda, and salt.
In a separate bowl, combine the buttermilk, oil, eggs, and vanilla extract.
Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Be careful not to overmix.
Slowly pour in the hot coffee, mixing until the batter is smooth. The batter will be thin.
Stir in the chocolate chips.
Pour the batter into the prepared pan.
Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached.
Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely.
Optional: Prepare a chocolate fudge frosting and spread it evenly over the cooled cake.
Optional Tips: For a more intense coffee flavor, add 1-2 teaspoons of instant espresso powder to the dry ingredients. Buttermilk can be substituted with 1 cup of milk mixed with 1 tablespoon of white vinegar; let sit for 5 minutes before using. For a richer flavor, use dark chocolate chips instead of semi-sweet.