In a medium bowl, heat-treat the flour by microwaving it for 1 minute to eliminate any bacteria. Let it cool slightly.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until smooth.
Add the vanilla extract and salt to the butter mixture, stirring until well combined.
Gradually mix in the heat-treated flour until fully incorporated.
Fold in the mini chocolate chips and sweetened condensed milk until the mixture is well combined.
Press the mixture evenly into a greased 8x8 inch baking pan.
Refrigerate for at least 1 hour to set before cutting into bars.