Heat oven to 350°F. Spray 13x9-inch pan with cooking spray. Break up cookie dough into pan. With floured fingers, press dough evenly in bottom of pan to form crust. Sprinkle 1 cup of the white chocolate chunks and the pretzels over dough; lightly press into dough.
Bake 16 to 20 minutes or until light golden brown. Cool completely on cooling rack, about 30 minutes.
In small microwavable bowl, place 1/4 cup of the white chocolate chunks; set aside. In large microwavable bowl, microwave remaining white chocolate chunks and the chocolate chips on High 2 minutes, stirring every 30 seconds, until melted and smooth. If necessary, microwave 30 seconds longer. Stir in peanut butter and cashews. Spread mixture evenly over cooled baked crust. Refrigerate until chocolate is set, about 15 minutes.
Microwave reserved 1/4 cup white chocolate chunks on High 30 seconds; stir until melted and smooth. If necessary, microwave 10 seconds longer. Drizzle over bars. Let stand until set, about 10 minutes. For bars, cut into 6 rows by 6 rows.