In a large bowl cream the butter and sugar. Add in the vanilla and mix well.
Stir in the flour and mix until combined.
Add in the sweetened condensed milk and cookie butter and stir until everything is mixed. Fold in the chocolate chips.
Place a piece of parchment paper in a 9 x 13 pan. Pour the batter into the pan and spread it to the edges. Refrigerate for 2 hours.
Heat the chocolate chips and cookie butter in a microwave safe container in 30 second intervals, stirring after each heating.
Pour over top of the cold cookie dough, spreading quickly over the top. Refrigerate for at least an hour.
Cut into small bars and serve.