In a large stand mixer, beat softened butter with brown sugar until fully combined.
Add vanilla and peanut butter, beat until fluffy.
Add flour and sweetened condensed milk.
Beat until everything is blended well. Fold in the chocolate chip morsels.
Press into an 8" x 8" tin foil baking tray.
Melt the chocolate chips add peanut butter in a double boiler or bowl on top of boiling water.
Melt for and mix until fully combined.
Pour over the cookie dough and spread evenly.
Refrigerate for 3 hours (or overnight). Cut into square pieces.
Serve and enjoy!