Preheat your oven to 350 degrees F. This is crucial to ensure even baking right from the start.
Prepare 2 or 3 8-inch cake pans by spraying them with baking spray. For a seamless release, cover the bottom with parchment paper and spray again. If you prefer thicker layers, use 2 pans; for thinner ones, use 3.
In a medium bowl, combine the dry ingredients: flour, sugar, baking powder, baking soda, and salt. Whisk them together to ensure they are well blended. This mixture will help the cake rise beautifully.
In a large bowl, mix the wet ingredients: eggs, vegetable oil, buttermilk, vinegar, mint extract, and gel food coloring. Using a hand mixer, whisk on medium speed until completely combined. The color should be a lovely minty green.
Reduce the mixer speed to low and slowly add in the dry ingredient mixture. Make sure to scrape the sides and bottom of the bowl occasionally. Mix just until everything is fully combined.
Gently fold in mini chocolate chips with a spatula. This adds delightful pockets of chocolate throughout the cake.
Divide the batter evenly into the prepared pans. This ensures that each layer bakes evenly.
Bake in the preheated oven, rotating the pans halfway through. Check for doneness by inserting a toothpick into the center; it should come out clean. For 2 layers, it will take about 30 minutes; for 3 layers, around 20 minutes.
Once done, remove the cakes from the oven and run a knife around the edges to loosen them. Let them cool in the pans for 20 to 30 minutes before inverting them onto a cooling rack. Allow them to cool completely before frosting.
For the frosting, melt the chopped semi-sweet chocolate in a microwave-safe bowl in 30-second increments, stirring after each. Let it cool to room temperature.
In a stand mixer, beat butter and half of the confectioners sugar until creamy. Gradually add the cooled chocolate and mint extract; mix until combined.
In a separate bowl, mix the remaining confectioners sugar and cocoa powder. Slowly add this to the frosting mixture, mixing on low until incorporated. Then increase the speed and beat for 1 to 2 minutes.
If your frosting is too thick, add a tablespoon of milk at a time until you reach the desired consistency. If it’s too runny, add more confectioners sugar.
Use a serrated knife to flatten the tops of the cooled cake layers, if needed. Place a small amount of frosting on the bottom of your cake stand to help secure the first layer.
Place the first layer on the stand, spreading about 1 cup of frosting on top. Use an offset spatula for a smooth finish.
Repeat with the next layer, adding frosting and stacking carefully. For a third layer, follow the same steps and cover the entire cake with the remaining frosting.
Decorate the sides and top of the cake with the remaining mini chocolate chips.
Refrigerate the decorated cake for at least 2 to 3 hours to set the frosting before serving.
For the ganache, heat whipping cream in the microwave until hot, about 40 to 60 seconds. Pour it over the chopped chocolate and let it sit for two minutes before stirring until smooth.
Allow the ganache to come to room temperature, then drizzle it over the chilled cake, starting from the center and letting it drip down the sides.
Refrigerate again for at least 30 minutes to let the ganache set.
To make whipped cream, combine cold heavy whipping cream with sugar, cocoa powder, and vanilla in a cold bowl. Whisk until stiff peaks form.
Transfer the whipped cream into a piping bag and frost the top of the cake. Chill before serving for the best texture.