In a large bowl mix together all the ingredients except for the chocolate chips
Stir in the chocolate chips
Pour batter into a buttered and floured cake pan
I used two 9-inch cake pans
For cooking time, use the cooking times on the back of the cake box as a guide and add about 10 minutes to that. Check for doneness using a tooth pick.)
Buttercream Frosting
In a mixer cream butter until fluffy
Add sugar and continue creaming until well blended
Add salt, vanilla, and whipping cream
Blend on low speed until moistened. and then beat at high speed until frosting is fluffy
Video
Notes
Don’t overbake the cake. Chocolate cake is best when it is moist and tender, so start checking it a few minutes before the recommended baking time. A toothpick inserted into the center should come out with a few moist crumbs rather than completely clean.
Use room-temperature ingredients. Allow refrigerated ingredients to come to room temperature before mixing. This helps everything combine more evenly and gives you a smoother batter and more tender cake.
Don’t overmix. Mix the batter just until everything is well combined. Overmixing can make your chocolate cake heavier and less tender.
Let it cool completely before frosting. Be sure your cake layers are completely cool before adding the frosting. Even a slightly warm cake can cause the frosting to soften or melt.
Make it ahead. The cake layers can be baked a day ahead. Once completely cool, wrap them tightly in plastic wrap and keep them at room temperature until you are ready to frost and assemble the cake.