Prepare a 9×9-inch baking tray by spraying it with nonstick cooking spray and layering it with a piece of parchment paper. Pour half of the peanut butter mixture into the baking tray and spread it out evenly. Add the melted chocolate to the remaining peanut butter mixture and mix thoroughly. Once incorporated, layer the chocolate mixture into the baking tray, over top of the peanut butter layer, and spread it evenly. Give the tray a few shakes and taps to remove any possible air bubbles and place the tray in the freezer for 1.5-2 hours to set.