Preheat oven to 375 degrees. Blend butter until smooth. Add egg and dry cookie mix, then blend mixture until dough is formed. Drop about one tablespoon of dough onto parchment lined cookie sheets, 2" apart.
Bake for 11-13 minutes, or until edges are golden brown. Cool on cookie sheet for 5 minutes then transfer to wire rack to cool completely.
Working with 7-10 cookies at a time, break up cookies into a large blender and pulse until they become the consistency of sand. Pour cookie crumbs into a large bowl and repeat with remaining cookies.
Place ice cream, milk, bananas and peanut butter into blender. Blend on high until smooth. Place two cups of cookie crumbs in blender and pulse to incorporate. Divide between four glasses. Garnish with remaining cookie crumbs.