In a medium microwave-safe bowl, add your all-purpose flour and microwave it on high for 1 minute. Let it cool slightly before moving to the next step.

In a large mixing bowl, combine the softened unsalted butter, packed brown sugar, and granulated sugar. Blend until smooth and fluffy, about 2-3 minutes.

Stir in the vanilla extract and a pinch of salt until well incorporated.

Gradually fold in the heat-treated flour until just combined. Be careful not to overmix.

Gently fold in the mini chocolate chips and sweetened condensed milk until well-mixed.

Transfer the mixture to a greased 8x8 inch baking pan, pressing down evenly and smoothing the top.

Cover the pan with plastic wrap and refrigerate for at least 1 hour to firm up.