01 - Preheat the oven to 350°F (175°C). Generously grease and flour a 12-cup Bundt pan, ensuring every crevice is coated to prevent sticking.
02 - In a large mixing bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt. Whisk until uniformly blended.
03 - Using a stand mixer fitted with the paddle attachment or a hand mixer, beat the softened unsalted butter and granulated sugar on medium-high speed until pale, light, and fluffy, approximately 3 to 4 minutes.
04 - Add the eggs one at a time, mixing thoroughly after each addition and scraping down the bowl as needed. Blend in the vanilla extract until fully incorporated.
05 - With the mixer on low speed, add the dry ingredient mixture alternately with the sour cream and whole milk in three additions, beginning and ending with the dry ingredients. Mix just until combined — avoid overmixing.
06 - Pour the batter into the prepared Bundt pan, spreading it evenly. Tap the pan firmly on the countertop a few times to release any trapped air bubbles.
07 - Bake on the center oven rack for 45 to 50 minutes, or until a wooden toothpick inserted into the thickest part of the cake comes out clean with only moist crumbs.
08 - Allow the cake to cool in the pan for 10 minutes. Gently invert onto a wire cooling rack and let it cool completely before glazing.
09 - In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer — do not boil. Pour the hot cream over the semi-sweet chocolate chips in a heatproof bowl. Let stand for 2 minutes, then stir from the center outward until a smooth, glossy ganache forms. Allow to cool slightly until it reaches a thick, drizzleable consistency.
10 - Place the cooled cake on a serving platter or over a wire rack with parchment underneath. Drizzle the ganache evenly over the top, letting it cascade naturally down the sides.
11 - Arrange candied cherries, cranberries, and green candied fruit in clusters around the top ring of the cake to resemble a holiday wreath. Tuck small sprigs of fresh rosemary or mint between the fruit for a greenery effect. Finish with a light dusting of powdered sugar to mimic fresh snow.