To make your cookie base, beat butter and brown sugar in mixing bowl until combined. Add peanut butter. Beat in egg and milk. Beat in the flour, salt and baking soda. Press dough into a 15x10x1 baking sheet lined with parchment paper or lightly greased.
Bake in a 375 degree oven for 15-18 minutes. Remove from oven.
Chop your Butterfingers candy bars into pieces. I chop the Butterfingers so that there are still some decent size pieces. I just like it better that way.
On stove top in small saucepan, heat sweetened condensed milk until warm. Add the chocolate and continue stirring until smooth. Pour fudge over cookie bars.
Top with crushed Butterfingers, pressing them into the fudge lightly. Allow to cool completely and cut into small bars.
*Depending on your oven, you may need to cook the cookie base for a little longer. It could take anywhere from 15-23 minutes depending on the oven. *The recipe turns out great whether you coarsely chop the Butterfinger or finely chop them.