Preheat the oven to 350°F; butter and flour dust 3X6-inch or 2X8-inch pans. Set them aside.
Sift all dry ingredients, and set them aside.
2½ cups All-purpose flour, 2½ teaspoon Baking powder, ½ teaspoon salt
Use the paddle attachment and cream the butter and sugar until light and fluffy.
1 cup Butter, 2 cups Sugar
Add the oil and mix well.
¼ cup Oil
Add the eggs one at the time and mix well after each addition. Add the vanilla extract and mix.
4 Eggs, 1 tablespoon Vanilla extract
Start adding the dry ingredients alternating with buttermilk. Start and finish with dry ingredients. Do not overmix.
1 cup Buttermilk
Use a rubber spatula and gently fold in the chocolate chips.
1½ cups Mini chocolate chips
Divide the batter between the prepared pan and bake for 35-40 minutes or until a tooth pick come out clean.
Let the cakes cool down in the pans, then transfer them to the cooling pan. Let them cool down completely before frosting.