My mother, eileen, has tried over 200 cookie recipes in her life. Of those, this recipe was one of our favorites. The sweet, chewy bars are like a magic trick in the oven as the marshmallows melt and turn golden brown.
Set the rack in middle of the oven and preheat to 350° F. Sift together dry ingredients flour, salt, and baking powder in a large mixing bowl. Butter a 9x13 pan. Set up a double boiler over low heat. In a small mixing bowl, beat the egg until frothy. If required, chop the walnuts.
Melt the butter and butterscotch chips in the double boiler over low heat. Cool slightly. In a large mixing bowl beat together the egg, vanilla, and brown sugar until fluffy. Gently fold in the butter and butterscotch chips and stir until smooth. Add the dry ingredients to the wet in thirds, blending until just combined after each addition. Fold in the marshmallows, chocolate chips and nuts. Scoop into the buttered 9 x 13 pan and spread evenly.
Bake at 350° for 20-25 minute DO NOT OVERBAKE! Let cool completely before cutting or storing. Makes 30 approximately 2” bars (cut 5 x 6).
Variations and Substitutions:
Use pecans instead of walnuts;.
Increase nuts to 1/2 cup for a nuttier experience;.
Add 3/4 cup of your favorite chips (white chocolate, peanut butter, or salted caramel).