How to Make It
Make the cake: Heat oven to 325° F. Butter a 14-cup Bundt pan. In a medium bowl, whisk together the flour, cocoa, salt, baking soda, and baking powder.
Using an electric mixer, beat the butter and sugar on medium-high until fluffy, 2 to 3 minutes. Beat in the vanilla, then the eggs, one at a time. Beat in the melted chocolate and chocolate syrup.
Reduce mixer speed to low. Add the flour mixture in 3 additions and the buttermilk in 2 additions, beginning and ending with the flour mixture. Mix just until combined (do not overmix).
Pour the batter into the prepared pan and bake until a toothpick inserted in the center comes out clean, 60 to 75 minutes. Let cool in the pan for 30 minutes, then invert onto a wire rack to cool completely.
Make the glaze: In a small saucepan, bring the cream just to a boil. Remove from heat, add the chopped chocolate, and let sit for 5 minutes. Whisk until smooth; let cool until slightly thickened, 10 to 15 minutes. Set the wire rack with the cooled cake over a rimmed baking sheet. Drizzle the cake with the glaze and let set before serving, 20 to 30 minutes.