Preheat the oven to 350 degrees F.
Line two large baking sheets with parchment paper and set aside.
Whisk together the flour, cocoa powder and baking powder in a medium bowl and set aside.
Add butter and 8 oz of bittersweet chopped chocolate to a small, microwave-safe bowl and melt in 30 seconds increments, stirring occasionally until smooth. Set aside to slightly cool.
In a large bowl, whisk together the eggs, vanilla, and granulated sugar until light and fluffy.
Add the slightly cooled melted chocolate mixture to the egg mixture and stir to combine.
Slowly add the flour mixture and stir until it is well combined. Chill for 30 minutes in the refrigerator.
In another medium bowl, mix powdered sugar with peanut butter until fully combined, then roll it into 1 inch balls. Making about 24 balls, arrange them on a cookie tray covered with waxed paper. Set aside.
Scoop about 1 1/2 - 2 tablespoons of dough onto the prepared baking sheets.
Bake for 10 minutes or until the cookies look firm on the outside, careful to not overbake!
Remove cookies from oven and immediately press lightly the peanut butter balls lightly into the center of each cookie. Cool the cookies for 5 minutes on the baking sheet, after that transfer to onto a cooling rack.
Melt the semisweet chocolate in 30 seconds increments using the microwave, and stirring after each round. Spoon melted chocolate over the peanut butter balls.
Chill for 10 minutes for the chocolate to settle and serve.