Preheat oven to 325ºF. Grease your pan and wipe out the excess.
Melt the butter and the chopped chocolate on low heat until smooth. Remove from the heat and add the sugars.
8 ounces bittersweet chocolate, ½ cups unsalted butter, 1 cup sugar, ¾ cup dark brown sugar
Mix the flour, cocoa powder, baking powder and salt into a bowl and set aside.
1 ¼ cups white whole wheat flour, ⅓ cup unsweetened cocoa powder, ½ teaspoon baking powder, ½ teaspoon kosher salt
While the chocolate/sugar mix is still warm, add in on egg at a time, stirring after each addition. Add the dry mixture spoonful by spoonful and mix until smooth.
4 whole eggs
Pour the batter into the pan and bake for 12-14 minutes. To see if the batter is fully cooked, stick a toothpick into the cake near the center of the circle. If the toothpick comes out clean, the cake is done.
Let cool for 10 minutes then transfer the cakes to a wire rack.
Glaze:
Sift the powdered sugar to break up and clumps. Add the milk, peanut butter and vanilla and stir until uniform.