Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by greasing them with oil and lining the bottoms with parchment paper.
In a large mixing bowl, whisk together the all-purpose flour, Dutch cocoa powder, baking powder, baking soda, and salt.
In a separate bowl, mix together the oil, vanilla extract, and eggs until well combined. Then add in the buttermilk and hot water.
Slowly pour the wet ingredients into your dry ingredients while mixing gently. Fold in half of the chopped Andes mints.
Divide your batter evenly between the prepared pans and bake for about 25 minutes or until a toothpick inserted into the center comes out clean.
While your cakes are cooling, beat together slightly cold unsalted butter with powdered sugar until fluffy. Gradually add in peppermint extract, vanilla extract, salt, and heavy cream.
Once your cakes are completely cooled, place one layer on a serving platter, spread frosting on top, and place the second layer on top. Use more frosting to cover the entire cake.