Preheat the oven to 300° F and grease one 9-inch round cake pan with either butter or cooking spray. In a medium bowl, sift together all of the dry cake ingredients (flour, sugar, cocoa powder, baking soda, baking powder, salt), and whisk to combine.

In a separate large bowl, whisk together the eggs, sour cream, canola oil, and vanilla extract until fully blended and creamy. Once combined, add in the dry ingredients and use a spatula or wooden spoon to mix - it will be very dry. Poor in the piping hot coffee and stir until fully combined (it'll look muddy and take some working). Add in the peppermint extract and chopped peppermint bark and stir to combine. Pour cake batter into the greased cake pan and bake for 30-40 minutes or until a knife inserted into the middle of the cake comes out clean.

Let the cake cool completely before crumbling it into a large bowl. While the cake is cooling, take your now-room-temperature butter and blend it the powdered sugar using an electric mixer. The mixture should be light and fluffy, give it a couple of minutes. Use a spatula to scrape all of the frosting into the bowl of cooled, crumbled cake, and use that same spatula to mix together the cake crumbles and the frosting until completely mixed into a squishy, solid mixture.

Cover a cookie sheet in parchment paper, and, using a tablespoon, measure out level scoops of the cake mixture and roll them into balls, placing them close together on the cookie sheet. Once all of the balls have been made, freeze them for at least 20 minutes before coating them in the chocolate.

While the cake balls are chilling, chop the chocolate into small chunks. In a heat-safe glass bowl microwave the chopped chocolate in 45 second intervals, stirring in between, until completely melted (usually 1:30 will do it). Using a fork, lower the cake balls into the melted chocolate until coated, then replace on a wire rack (over a tray to catch drips), continuing until all the cake balls are coated. If you want to add crushed peppermints to the top of the truffles, do so right after coating them in chocolate before the coating hardens.

Once complete, serve! Or store in the fridge or freezer for up to a week!