Preheat oven to 350°.
Combine flour, sugar, cocoa, baking soda, baking powder, and salt in a bowl and set aside.
Melt coconut oil and set aside, allowing a few minutes for it to cool off.
Meanwhile, combine milk, applesauce, vinegar, vanilla, and peppermint in a separate bowl.
Combine wet and dry ingredients into one bowl, adding the coconut oil in last and stir with an electric mixer until everything is combined.
Grease 3 6" cake pans with coconut oil and distribute batter evenly into cake pans.
Place pans in the oven and bake for 35-45 minutes, or until a toothpick comes out clean.
Allow cakes to sit in cake pans for 10 minutes before carefully transferring them to a cooling rack. Wait until cakes have completely cooled before icing them.
For the ganache: Chop chocolate (if using chocolate chips, keep them as-is), place in a bowl and set aside.
Heat coconut milk in a saucepan over medium-high heat until it starts to bubble. You don't want it to boil--as soon as you see bubbles forming, pour the milk overtop of the chopped chocolate.
Wait 5 minutes, add the vanilla and peppermint, and then use a spatula to stir everything together. Slowly but surely the chocolate will melt. Wait until chocolate has cooled and then place a lid or cling wrap overtop of bowl and allow chocolate to sit out for at least four hours, allowing chocolate to harden a bit. You want the chocolate to be pretty thick but still spreadable.
To assemble: Carefully slice the domes off of each cake. Place a large dollop of ganache on one cake and spread it on top. Next, place a second cake overtop of the icing and repeat the process. Last, place several dollops of ganache on the side of the cake and use an uneven spatula to smooth icing all over the cake.
If you want to add the top layer of ganache dripping down, repeat the same process as you did the first time around but this time pour the ganache over the cake right away (rather than letting it sit out to harden).