Preheat the oven to 350° F. Spray a 12-cup Bundt pan with non-stick baking spray.
In a medium bowl, mix the flour, sugar, baking soda, and salt.
In a separate microwave-safe bowl, heat butter in the microwave until fully melted. Add in the milk and cocoa powder. Whisk until well combined.
Add the chocolate mix to the dry ingredients, then stir until fully combined. The batter will be thick.
Add in the eggs, making sure to fully combine. Add the sour cream, oil, and vanilla. Mix until batter is combined and smooth. Gently fold in the ½ cup chopped peppermint bark.
Pour the batter into the prepared Bundt pan and bake for 45 to 55 minutes or until a toothpick inserted into the middle of the cake comes out clean.
To make the ganache
Heat the heavy cream in a microwave-safe bowl in 30-second increments until hot. Carefully remove from the microwave and add in the semi-sweet chocolate. Allow to sit for 3 to 5 minutes then stir until smooth.
Once the cake is done, flip it onto a plate and allow it to cool completely (DO NOT SKIP THIS STEP). Drizzle ganache over the cooled cake and top with the remaining ½ cup peppermint bark.