Microwave the butter in a microwave-safe bowl on 30% power for about 30 seconds until melted and fragrant.
Add the brown sugar and vanilla extract to the melted butter. Stir with a spatula until the mixture is smooth, glossy, and the sugar begins to dissolve.
Pour in the rolled oats and mini chocolate chips, folding gently to combine and distribute evenly throughout the mixture.
Stir in the sweetened condensed milk vigorously until the mixture becomes thick, glossy, and cohesive—this helps everything stick together.
Using a small cookie scoop or tablespoon, portion out the mixture and roll into compact balls about 2 inches in diameter.
Place the cookie dough bites on a parchment-lined tray or plate, spacing them slightly apart.
Chill the bites in the freezer for at least 30 minutes until firm and set, which makes them easier to handle and enhances their chewy texture.
If desired, melt a few more chocolate chips and drizzle over the chilled bites for extra visual appeal. Let them set for about 10 minutes at room temperature.
Serve the cookie dough bites straight from the fridge or at room temperature for a soft, chewy, and indulgent treat that tastes just like raw cookie dough.