Preheat oven to 350°.
Put the Fritos and the pretzels in a large Ziploc bag and smash until broken, but not crumbs. Set aside.
Line a 9" x 13" pan or cookie sheet with Release foil or parchment paper.
Lay the Frito/pretzel mixture flat, but tightly packed, across the lined pan. Set aside.
Place butter and peanut butter in a saucepan and melt over medium heat. When mixture is melted, stir in brown sugar. Bring mixture to a boil and boil for 1 minute, stirring once or twice. Pour over Frito mixture.
Bake in the oven for 8 minutes. Remove pan from oven and sprinkle chocolate chips over hot candy. Return to oven for 1 minute to soften chips. Spread softened chocolate chips over the candy and sprinkle the peanut pieces on top (pressing them into the chocolate.)
Cool at room temperature until the pan is cool enough to transfer into your refrigerator. Keep the pan in the refrigerator at least an hour. When chocolate is set, lift from pan and break the candy into pieces. Eat it cold or at room temp.