Spray an 8x8-inch metal pan with nonstick cooking spray, then line with parchment paper, leaving overhang on all sides. Grease the parchment with a bit more nonstick cooking spray.

Preheat the oven to 350 degrees F.

Combine ¼ cup of cocoa powder, chopped chocolate and espresso powder in a heatproof bowl. Set aside.

Melt the butter in a small sauce pan, and gently boil it (bubbles!) for 3-4 minutes.

Pour the melted butter over the chocolate/espresso mixture, and let stand for 2 minutes. Then, whisk to thoroughly combine. Set aside.

Combine the sugar, brown sugar, eggs, vanilla extract, and salt in a large bowl, and beat with an electric mixture for about 8 minutes. The mixture will be thick and slightly glossy. Stream in the melted chocolate/butter mixture with the hand mixer on low speed, and beat for another minute, until smooth.

Sift in the flour and remaining cocoa powder. Use a large wooden spoon or rubber spatula to gently fold the dry ingredients in. Pour the brownie batter into the prepared pan, and use an offset spatula to make sure the top is even.

Spoon large dollops of the room temperature peanut butter on top of the batter. Use a small, sharp knife to create a marbled pattern. Sprinkle the chopped candy-coated peanut candies on top.

Bake at 350 degrees for about 30-35 minutes. Sprinkle with flakey sea salt.  Allow to cool completely, the lift the brownies out of the pan using the parchment overhang, and slice with a sharp chef's knife.