1. Preheat oven to 350 degrees. Line an 8-inch square baking pan with foil so that the foil comes up the sides of the pan and overhangs slightly.
2. In a medium saucepan over medium-low heat, melt the butter. When it's melted, remove the pan from the heat and whisk in the sugars and peanut butter until the ingredients are all incorporated. Let stand to cool slightly, about 5 minutes.
3. In a large mixing bowl, whisk the eggs, then whisk in the vanilla. When the peanut butter mixture has cooled, stir it into the eggs until smooth and incorporated. Stir in the flour and salt until incorporated, then stir in the chocolate chunks and peanut butter chips.
4. Spread the batter in the prepared pan, smoothing the top. Bake for 30 to 35 minutes, until just set. Place on a rack to cool.
5. When the brownies are cool, turn out onto a cutting board. Peel off foil, turn brownies over, and slice into 16 squares. Brownies will keep for several days stored in an airtight container.
Source: Hannaford fresh Magazine, January - February 2011