Spread flour on a microwave-safe plate and microwave in 30-second intervals, stirring between each, for about 1 minute total until it reaches 165°F inside. Let cool.
Beat softened butter and brown sugar together until fluffy.
Mix in milk, vanilla, and salt, then stir in the cooled heat-treated flour until a dough forms.
Fold in mini chocolate chips and M&Ms.
Roll into 1-inch balls and place on a parchment-lined sheet.
Refrigerate for 30 minutes until firm, then store in an airtight container in the fridge.
