Preheat the oven to 350ºF (175ºC) and position the rack just above the center. Prepare 2, 8-inch cake pans by spraying them with a flour-based baking spray. Optionally, line the pans with parchment paper circles and cake strips to ensure easy removal.

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside 2-3 tablespoons of this mixture to coat the mini chocolate chips, which helps prevent them from sinking in the batter.

In a large bowl, cream the unsalted butter and granulated sugar until light and fluffy. Add the eggs, vegetable oil, vanilla extract, and whole milk, mixing until well combined.

Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Fold in the coated mini chocolate chips, ensuring that they are evenly distributed throughout the batter. The batter should be thick but spreadable.

Divide the batter evenly between the prepared cake pans. Bake for 32-35 minutes or until a toothpick inserted into the center comes out clean. Allow the cakes to cool for 10 minutes in the pans before transferring them to wire racks to cool completely.

For the frosting, beat the unsalted butter in a large bowl until smooth. Gradually add the sifted powdered sugar, mixing until well combined. Then, mix in the vanilla extract and heavy cream until the frosting is light and fluffy. Fold in the mini chocolate chips for added texture and flavor.

Once the cakes are completely cooled, generously frost the tops and sides with the chocolate chip buttercream frosting, creating a beautiful and delicious layer of frosting.