Prepare the Mini Cakes

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 12-cup muffin tin or line with paper liners.
2. Mix Dry Ingredients: In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
3. Cream Butter and Sugars: In a large mixing bowl, use a hand or stand mixer to beat the butter, granulated sugar, and brown sugar until light and fluffy.
4. Add Eggs and Vanilla: Beat in the eggs one at a time, then mix in the vanilla extract.
5. Combine Wet and Dry: Alternate adding the dry ingredients and buttermilk to the butter mixture, beginning and ending with the dry ingredients. Mix until just combined.
6. Fold in Cranberries: Gently fold in the chopped cranberries.
7. Fill the Pan: Spoon the batter evenly into the prepared muffin tin, filling each cup about two-thirds full.
8. Bake: Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
9. Cool: Allow the cakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

Prepare the Glaze

1. Melt Chocolate: In a microwave-safe bowl, combine the chocolate chips, heavy cream, and butter. Microwave in 20-second intervals, stirring between each, until smooth.
2. Cool Slightly: Let the glaze cool for 5 minutes to thicken slightly.

Decorate the Cakes

1. Glaze the Cakes: Spoon or drizzle the glaze over the cooled cakes, allowing it to drip down the sides for a rustic look.
2. Add Garnish: Top each cake with a whole cranberry and a light dusting of powdered sugar, if desired.