01 - Preheat oven to 350°F (175°C). Generously grease and flour a 10-cup Bundt pan, ensuring every crevice is coated to prevent sticking.
02 - In a medium bowl, sift together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt. Set aside.
03 - In a large mixing bowl, beat the room-temperature unsalted butter and granulated sugar together using an electric mixer on medium-high speed until pale, light, and fluffy, approximately 3 minutes.
04 - Add the large eggs one at a time, beating thoroughly after each addition until fully incorporated. Blend in the vanilla extract until combined.
05 - Alternately add the sifted dry ingredient mixture and the buttermilk to the butter-sugar mixture, beginning and ending with the dry ingredients. Fold gently until just combined — avoid overmixing to keep the crumb tender.
06 - Pour the batter evenly into the prepared Bundt pan. Use a spatula to smooth the top and tap the pan gently on the counter to release any trapped air bubbles.
07 - Bake on the center rack for 45–50 minutes, or until a wooden skewer inserted into the thickest part of the cake emerges clean and the top springs back lightly when touched.
08 - Allow the cake to rest in the Bundt pan for 15 minutes to set. Carefully invert onto a wire cooling rack and let cool completely before glazing.
09 - In a small saucepan, heat the heavy cream over medium heat until just steaming — do not boil. Place the semisweet chocolate chips and unsalted butter in a heatproof bowl, pour the hot cream over the top, and let stand for 2 minutes. Whisk until silky and smooth.
10 - Position the cooled cake on the wire rack set over a sheet of parchment paper. Drizzle the chocolate glaze generously over the cake, allowing it to cascade naturally down the sides.
11 - Lightly dampen the fresh cranberries with water, then roll them in granulated sugar until evenly coated. Let dry on a wire rack. Arrange the sugared cranberries and fresh rosemary sprigs artfully around the top of the glazed cake to resemble a holiday wreath. Finish with a light dusting of powdered sugar for a snowy effect.