Add Wet Ingredients & Cocoa: Add the buttermilk, sour cream, and eggs, mixing until well combined. Sift in the cocoa powder and mix until fully incorporated.
Add Dry Ingredients: Add the flour, baking powder, and baking soda, mixing on low speed just until combined and no flour pockets remain.
Bake: Pour the batter into your prepared loaf pan and smooth the top with an offset spatula. Bake at 180°C (320°F) for 55 to 65 minutes, or until a toothpick inserted into the center comes out clean. Remove from the oven and let cool completely on a wire rack.
Make the Ganache: Heat the heavy cream in a saucepan over medium heat until it begins to gently simmer. Pour the hot cream over finely chopped chocolate in a heatproof bowl.
Let it sit undisturbed for 5 minutes, then whisk gently from the center outward until glossy and smooth.
Glaze and Serve: Pour the chocolate ganache over the cooled cake, spread evenly with an offset spatula, slice, and enjoy!
Notes
Room-Temperature Ingredients: Ensure your butter, eggs, sour cream, and buttermilk are fully at room temperature so the batter emulsifies properly into a smooth, homogeneous mixture.
Measure Flour Correctly: Fluff your flour with a spoon, scoop it into your measuring cup, and level it off with a knife to avoid packing too much flour and drying out the cake.
Cream Thoroughly: Beating the butter, sugar, salt, and vanilla together until light and fluffy (2 to 3 minutes) is crucial for building a tender, velvety crumb.
Do Not Overmix: Once you add the dry ingredients, mix just on low speed until combined to prevent developing excess gluten, which can make the cake dense.
Cool Completely Before Glazing: Ensure the pound cake is completely cool on a wire rack before pouring the warm chocolate ganache over it to prevent the topping from melting or sliding off.