Heat oven to 375°F. In large bowl, stir together cookie mix and crumbs. Stir in melted butter until soft dough forms. Press into greased 13x9 inch pan.
Bake 18 to 20 minutes or until set. Immediately sprinkle chocolate chips over crust. Let stand 3 to 5 minutes or until chocolate begins to melt. Spread chocolate evenly over crust.
Set oven control to broil. Sprinkle marshmallows over melted chocolate. Broil with top 4 to 5 inches from heat 20 to 30 seconds or until marshmallows are toasted. Marshmallows will brown quickly so don't look away too long! Cool 10 minutes. We cut into 6 rows by 5 rows. Serve warm. Store any remaining bars tightly covered.
Add a sweet grandson who loves to cook with Gramma and you have a memory in the baking :-)