Preheat your oven to 350°F (175°C) and prepare three 8-inch round cake pans by greasing them and lining the bottoms with parchment paper for easy removal.
In a large mixing bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt. This ensures an even and lump-free mixture.
In a separate bowl, whisk the buttermilk, hot water or coffee, vegetable oil, both sugars, eggs, peppermint extract, and vanilla extract until the mixture is smooth and well combined.
Gradually incorporate the dry ingredients into the wet mixture, stirring just until the batter is smooth and no streaks of flour remain. Avoid overmixing to keep the cake light and tender.
Evenly divide the batter among the prepared cake pans and bake for 25–30 minutes. Check for doneness by inserting a toothpick into the center; it should come out clean or with a few moist crumbs.
Allow the cakes to cool in the pans for about 10 minutes, then turn them out onto a wire rack to cool completely before frosting.
In a large bowl, beat the softened butter with an electric mixer until it becomes light and creamy.
Gradually add the powdered sugar, a little at a time, mixing on low speed to prevent a sugar cloud.
Pour in the heavy cream, peppermint extract, vanilla extract, and a pinch of salt. Increase the mixer speed to medium-high and beat until the frosting is fluffy and easy to spread. Adjust the consistency with more cream if needed.
Place one cake layer on a serving plate or cake stand. Spread an even layer of frosting on top using an offset spatula.
Repeat with the second layer, then the third, stacking the cakes carefully. Coat the entire cake with a thin crumb coat of frosting to seal in any loose crumbs.
Refrigerate the cake for 20 minutes to set the crumb coat, then apply the final layer of frosting for a smooth and polished finish.
Gently press crushed candy canes into the sides of the cake to create a festive border.
Top the cake with whipped cream swirls, mini meringues, peppermint bark pieces, and white chocolate shavings for a showstopping presentation.
Sprinkle additional crushed peppermint candies over the top for added texture and holiday flair.
Slice the cake into generous portions and serve at your holiday gathering. The refreshing peppermint flavor and rich chocolate layers make this dessert a memorable centerpiece for the season!