Double-Chocolate Loaf with Peanut Butter Cream Cheese Spread

Ingredients

• ¾ cup firmly packed dark brown sugar
• 1 cup dark unsweetened coco powder (like Valrhona), sifted
• 1½ cups all-purpose flour
• ¾ cup granulated sugar
• 1½ tsp baking soda
• ¾ tsp baking powder
• 1 tsp salt
• 2 large eggs
• 1 large egg yolk
• ¾ cup buttermilk
• ½ cup vegetable oil
• 1 tsp pure vanilla extract
• 8 ounces good-quality dark chocolate (60-72%), coarsely chopped
• 5 ounces cream cheese, softened
• 2 Tb creamy peanut butter
• ⅓ cup sugar