In a large mixing bowl, beat softened butter with brown sugar until well combined. Add vanilla and peanut butter, beat until fluffy. Add flour and sweetened condensed milk. Beat until everything is well blended. Fold in mini chocolate chips.
Press into a wax paper lined 8x8 glass baking dish.
Melt 3/4 cup creamy peanut butter and 3/4 cup chocolate chips, stirring until well melted/combined.
Refrigerate until firm. Cut into bite size pieces. Store in a covered container.