In a food processor, pulse the rolled oats until they reach a coarse flour-like consistency, about 10-15 pulses. Set aside.
In a microwave-safe bowl, heat the all-purpose flour for 1 minute on high to heat-treat it, then let it cool completely.
In a large mixing bowl, beat the softened unsalted butter, light brown sugar, and granulated sugar together until creamy and smooth, about 2-3 minutes.
Add the vanilla extract and milk to the butter mixture and mix until combined.
Add the heat-treated flour, oat flour, and salt to the wet ingredients. Stir until fully incorporated and a dough forms.
Fold in the mini chocolate chips evenly throughout the dough.
Serve immediately or store in an airtight container in the refrigerator for up to 5 days.