1Heat oven to 350°F (if using dark or nonstick pan, heat oven to 325°F). Grease bottom and sides of 13x9-inch pan with shortening or spray with cooking spray.
2In large bowl, beat brown sugar, butter, peanut butter, vanilla and eggs with electric mixer on medium speed, or mix with spoon, until well blended. Stir in flour, baking powder, baking soda and salt. Cut 12 of the candies into fourths (about 3/4 cup). Stir cut-up candies and chocolate chips into batter. Spread in pan.
3Bake 25 to 30 minutes or until golden brown. Immediately press remaining 24 candies in brownies in 4 even rows of 6 candies each. Cool completely, about 1 1/2 hours. For brownies, cut into 6 rows by 4 rows.