Preheat oven to 350°F. In bowl of stand mixer (or a large bowl if using a handheld mixer), cream together peanut butter and sugar until well blended. Beat in eggs and vanilla.
Press peanut butter cookie mixture into greased 13x9-inch pan. Place whole sandwich cookies on top of peanut butter cookie layer.
Prepare brownie mix as directed on package, adding cinnamon. Pour brownie batter evenly over sandwich cookie layer.
Bake 35 to 40 minutes, or until a toothpick, inserted in brownie layer only, comes out with fudgy crumbs. Cool in pan 10 minutes.
Meanwhile, for the Peanut Butter Sauce, melt butter and peanut butter in medium saucepan on medium-low heat. Add butterscotch chips. Remove from heat and stir until mostly melted. Cool slightly. Cut brownies into bars. Pour Peanut Butter Sauce over brownies!