1. Preheat the oven to 350°F. Grease a 12-cup bundt pan and lightly coat with cocoa powder. Tap out any excess.
2. In a large saucepan, combine the stout, chopped dark chocolate, and butter. Heat over medium-high, stirring, until the butter and chocolate are fully melted and combined. Stir in the cocoa powder until smooth. Remove from heat and allow to cool to room temperature.
3. Beat the eggs into the cooled chocolate mixture, stirring vigorously for about 3 minutes until well combined.
4. Beat in the brown sugar and granulated sugar. Fold in the yogurt until fully incorporated.
5. Stir in the flour, baking soda, and salt. Mix just until combined.
6. Pour the batter into the prepared bundt pan and smooth the top.
7. Bake for 50–55 minutes, or until a toothpick inserted in the center comes out clean.
8. Remove from the oven and cool in the pan for 15 minutes. Tap all around the sides and bottom to loosen, then turn out onto a wire rack to cool completely to room temperature.

Chocolate Stout Ganache

1. Pour the stout into a small saucepan and cook over medium heat until reduced to a thick, syrupy glaze, about 8–10 minutes.
2. Add the heavy cream and heat, stirring, until the mixture is steaming hot and combined.
3. Remove from heat, add the finely chopped chocolate, and let sit undisturbed for 5 minutes.
4. Gently stir until the ganache is completely smooth and glossy.
5. Pour the warm ganache over the fully cooled cake. Allow to set for 10 minutes before slicing. The cake keeps in an airtight container at room temperature for about 7 days.