Preheat the oven to 325 degrees. Spray an 8x8 baking dish with non-stick spray.
In the bowl of a stand mixer, beat together brown sugar, peanut butter, eggs and vanilla until combined.
1 cup brown sugar, ¾ cup creamy peanut butter, 2 eggs, 1 tablespoon vanilla
Add in the baking mix and salt, mixing until combined, then add in the Reese’s Pieces and mini chocolate chips. The mix will be very thick, you may need to mix in by hand.
2 cups baking mix, ½ teaspoon salt, 6 oz. Reese’s Pieces candy, 1 cup mini chocolate chips
Spread into the prepared baking dish in an even layer.
Bake for 40-45 minutes or until the center is set.
Allow to cool, then cut into squares.