Melt butter & marshmallows in a large teflon pot over medium heat, stirring constantly. Add butterscotch chips & stir until melted. Remove from heat.
Add rice cereal & fold into marshmallow mixture.
In a greased 9x13" pan, pour krispies mixture. Roll flat with a rolling pin, sprayed with pan spray to prevent sticking.
In a separate small saucepan over medium-low heat, melt chocolate chips & peanut butter until smooth, stirring constantly to prevent burning the chocolate. Pour over the rice krispies & smooth with a spatula. Let set at room temperature for a couple hours.
*The topping doesn't harden like plain melted chocolate would, it's more like a ganache, & will be soft but you want to wait until it is solid enough to cut. If you are in a rush, cover & place in the refrigerator for 30 minutes, but keep an eye on it because refrigeration can cause your krispies to dry out.