Spray 2 or 3 8-inch cake pans with baking spray, cover the bottom to fit with parchment paper and spray again with baking spray. Use 3 pans for thinner layers and 2 for thicker layers. Set aside.
In a medium bowl combine dry ingredients: flour, sugar, baking powder, baking soda, and salt. Whisk to combine. Set aside.
Add wet ingredients to a large bowl: eggs, oil, buttermilk, vinegar, mint extract, and green gel food coloring. Using a hand mixer (or stand mixer), whisk on medium speed until fully combined.
Reduce mixer speed to low, and slowly add the dry ingredients mix. Stop from time to time to scrape the sides and bottom of the bowl. Whisk just until fully combined.
Stir in mini chocolate chips with a spatula.
Divide the batter equally into the prepared pans.
Bake, rotating the pans halfway through the cooking process until a toothpick inserted into the center of the cakes comes out clean. About 30 minutes for 2 layers and about 20 minutes if the batter is divided into 3 layers.
Remove the cakes from the oven and run a knife around the edges to loosen them from the pans. Let it cool in the pans for about 20-30 minutes. Invert the cakes onto a plate and then re-invert them onto a cooling rack. Round side up. Cool completely before frosting.
Add chopped chocolate to a microwave safe bowl and melt it in the microwave in 30 seconds increments, stirring after each one to make sure it doesn't burn. Cool to room temperature.
Add butter and half of the confectioner's sugar to the bowl of a high-speed stand mixer. Beat, starting on low speed, then increasing the speed gradually to medium-high.
Turn the mixer off and add in cooled chocolate and mint extract, beat on medium speed until combined, for about 30 seconds.
In a medium bowl combine remaining confectioners sugar and cocoa powder.
Turn mixer on to the lowest setting and add in confectioners sugar and cocoa mixture, 1 cup at a time. Once incorporated, turn mixer on high for 1-2 minutes.
If the mixture is too thick add 1 tablespoon of whole milk at a time. If the mixture is too runny, and won't hold its shape, add more confectioners sugar, ½ cup at a time.
Frost the Cake:
Using a serrated knife or cake leveler, slice the layer's top to make them flat.
Add 1/4 cup of frosting onto the bottom of a cake stand.
Place the first layer onto the cake stand. Add about 1 cup (or more if needed) of frosting onto it and using an offset spatula, spread the frosting evenly, to create a 1/2-inch layer.
Add another layer on top and repeat. Add the third layer if using and cover the entire cake with the remaining frosting.
Use the mini chocolate to garnish the sides and top edges of the cake.
Refrigerate for at least 2-3 hours, or until somewhat stiff before serving.
Heat whipping cream in the microwave for 40-60 seconds until hot.
Place chopped chocolate into a bowl and pour hot whipping cream on top. Let it sit for two minutes and then stir until smooth and shiny.
Let the ganache come to room temperature (very important) for about 10 minutes before drizzling over the cake. Start in the center and let the ganache drizzle over the sides of the cake.
Refrigerate for at least 30 minutes, until ganache is settled.
Chocolate Whipped Cream:
Add heavy whipping cream to a cold bowl (I usually refrigerate it for 15 minutes), add sugar, cocoa and vanilla extract and whisk on slow-medium speed, gradually increasing to high speed. Whisk until stiff peaks form and the whipped cream holds its shape.
Add the whipped cream to a piping bag fitted with a star tip and frost the cake.