For the cake:
Adjust your oven rack to the 2nd level position (just above center) and preheat to 350ºF (175°C).
Spray two 8-inch cake pans with a flour-based baking spray and set aside. You can also add parchment paper circles or cake strips for better results.
In a medium-sized mixing 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 later.
In a large bowl, beat together the unsalted butter and granulated sugar until light and fluffy. Add in the eggs, vegetable oil, vanilla extract, and milk. Mix until smooth and well combined.
Gradually add the dry ingredients (excluding the 2-3 tablespoons reserved) to the wet ingredients. Mix until just combined. Fold in the mini chocolate chips coated in the reserved dry mixture.
Evenly distribute the batter into the prepared cake pans. Bake side by side for 32-35 minutes, or until a toothpick inserted comes out clean.
Once baked, allow the cakes to cool in the pans for 10 minutes. Then invert them onto wire cooling racks to cool completely before frosting.
For the chocolate chip buttercream frosting:
Beat the unsalted butter on medium-high speed using a hand mixer or stand mixer with a paddle attachment until smooth (about 2-3 minutes).
On low speed, gradually add the sifted powdered sugar, one cup at a time, until well blended. Add the vanilla extract and heavy cream.
Stir in the mini chocolate chips using a spatula. If you’re making the frosting in advance, wait to add the chocolate chips until you’re ready to frost the cake.
Enjoy your delicious chocolate chip cake!