Preheat oven to 350. Line an 8-inch square baking dish with parchment or foil, leaving an overhang on two sides. Spray foil with non-stick cooking spray.
Heat the chocolate in a small microwave safe bowl, stirring every 30 seconds until melted.
In a medium bowl, whisk together flour, cocoa powder, salt, and baking soda. In another bowl, whisk together brown sugar, applesauce, sour cream, melted chocolate, eggs and oil until combined. Add in flour mixture and mix until just moistened. Do not overmix!
Spread batter in prepared pan. Sprinkle evenly with peanut butter chips. Bake for 30 to 35 minutes, or until a toothpick inserted in the center comes out with just a few moistened crumbs.
Cool completely in pan. Using foil overhang, lift brownies out of pan. Remove foil and cut into squares.