• Preheat your oven to 350°F (175°C). Grease and flour two 8-inch round cake pans to prevent sticking.
• In a large mixing bowl, combine all dry ingredients: flour, sugar, baking powder, baking soda, and salt. Whisk by hand for about 30 seconds to ensure they are thoroughly combined.
• In a separate bowl, whisk together the eggs, buttermilk, and vanilla extract until smooth.
• With your mixer set to low speed, gradually add small portions of softened butter into the dry ingredients, mixing until the butter coats the flour mixture, forming a crumbly and moist consistency. Increase speed to medium, scraping down the bowl as needed.
• Pour in half of the egg mixture, mixing on medium speed for 1 ½ minutes (avoid exceeding medium speed), which will yield a thick and airy batter. Scrape the bowl thoroughly before adding the remaining egg mixture in two parts, beating for about 20 seconds after each addition.
• Gently fold in the chocolate chips, ensuring even distribution throughout the batter.
• Divide the batter evenly between the prepared pans. Bake for 30-35 minutes or until a toothpick inserted in the center comes out mostly clean, with only a few crumbs attached.
• Allow the cakes to cool in the pans for about 10 minutes before carefully turning them out onto a wire rack to cool completely.

For the Chocolate Buttercream

• Begin by beating the softened butter on low to medium speed until smooth. Blend in the vanilla extract, and then gradually add the powdered sugar, cocoa powder, and salt.
• Pour in most of the milk. Start the mixer on low speed to prevent the powdered sugar from creating a dust cloud, then increase speed as the frosting begins to combine.
• Mix for 5-6 minutes or until the frosting reaches a smooth, spreadable consistency. If using a hand mixer, it may take longer. Adjust by adding more milk (1 tablespoon at a time) if too thick, or additional powdered sugar if too soft. You should end up with about 7 cups of buttercream.

For the Vanilla Buttercream Filling

• Cream the slightly softened butter until smooth, then blend in the vanilla extract.
• Gradually add the powdered sugar and milk, mixing on medium speed until light and fluffy, about 1-2 minutes. Adjust the consistency by adding more powdered sugar if it needs to be thicker or a bit more milk if it needs thinning.
• Gently fold in a handful of mini chocolate chips for a delightful texture.