Be sure to heat-treat the flour and allow it to cool before using in this recipe. You can spread it on a baking sheet and bake at 350°F or heat it in the microwave for about 1 minute and 30 seconds, stirring every 20 seconds to prevent it from burning. Allow to cool completely before using to avoid melting the butter. Cooking the flour kills bacteria and makes it safe to eat in the frosting.
Add the butter to the bowl of a stand mixer. Beat with the paddle attachment until smooth. Add in the brown sugar and beat again for 2-3 minutes on medium-high.
Scrape down the sides and bottom of the mixer and add the powdered sugar. Mix on low until incorporated, increasing the speed to medium-high to beat it further.
Add the flour and salt and beat on low until incorporated. Add 3 tablespoons of milk and the vanilla. Beat on medium speed until combined and fluffy. If the frosting is too stiff, add 1-2 more tablespoons of milk and beat again until smooth and light.
Fold in the mini chocolate chips by hand.
Use to frost your favorite desserts! If frosting cupcakes, avoid using any piping tips other than a very large round tip. The chocolate chips will clog star tips.