Calling All Chocolate and Peanut Butter Lovers: Buckeye Brownies Await!

Name: Calling All Chocolate and Peanut Butter Lovers: Buckeye Brownies Await!
Ingredients: Cooking spray; 2 sticks unsalted butter (226g; 1 cup); 7 ounces granulated sugar (198g; 1 cup); 5 1/4 ounces packed light brown sugar (148g; 3/4 cup); 7 ounces bittersweet (70 to 75%) dark chocolate, chopped (200g; about 1 1/4 cups), divided; 2 1/2 ounces Dutch-processed cocoa powder (70g; about 2/3 cup); 3 tablespoons (45ml) strong brewed coffee; 1 tablespoon (15ml) vanilla extract; 1 1/4 teaspoon kosher salt; for table salt use half as much by volume; 3 large eggs, room temperature; 4 1/2 ounces all-purpose flour (127g; 1 cup); 2 sticks unsalted butter (226g; 1 cup), at room temperature; 1 cup creamy peanut butter (9 1/2 ounces; 269g), (see notes); 10 ounces confectioners' sugar (283g; 2 1/2 cups); 2 tablespoons (30ml) heavy whipping cream; 1 1/2 teaspoon vanilla extract; 1/2 teaspoon kosher salt; 4 1/2 ounces bittersweet (72% dark) chocolate, chopped (127g; about 3/4 cup); 1/2 cup (120ml) heavy whipping cream; 1/2 tablespoon unsalted butter; 1/4 teaspoon kosher salt; for table salt, use half as much by volume; Flaky sea salt for sprinkling