Preheat the oven to 350°F (175°C) and prepare two round cake pans.
In a large mixing bowl, whisk together the dry ingredients: flour, cocoa powder, baking powder, baking soda, and salt.
In another bowl, combine the sugars, oil, eggs, coffee, vanilla, and peppermint extract; mix well.
Gradually add the wet mixture to the dry ingredients, stirring until just combined.
Divide the batter evenly between the prepared pans and smooth the tops.
Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.
Once baked, allow the cakes to cool in the pans for about 10 minutes before transferring them to wire racks.
While the cakes cool, prepare the frosting by whipping the heavy cream until soft peaks form, then gradually add powdered sugar and peppermint extract, mixing until smooth and fluffy.
Once the cakes are completely cool, place one layer on a serving plate and spread a layer of frosting on top.
Place the second cake layer on top and frost the top and sides of the entire cake.
Decorate the top with crushed peppermint candies for a festive touch.