2 cups / 475 ml chocolate porter or stout beer 8 tablespoons unsalted butter, plus more for the pan 3/4 cup / 75
g natural cocoa powder (non-dutched) 1 cup / 5 oz / 140
g whole wheat flour 1 cup / 4.5 oz / 125
g all - purpose flour 1 cup / 4.25 oz / 120
g muscovado or
dark brown sugar 1 1/2 teaspoons baking soda 3/4 teaspoon fine grain sea salt 3 large eggs 1 1/2 cups / 355 ml plain whole yogurt 3/4 cup / 180 ml pure maple syrup