01 - Beat softened butter and brown sugar with electric mixer on medium speed until light and fluffy, approximately 2 minutes.
02 - Pour in milk and vanilla extract, beating until fully incorporated and mixture appears smooth.
03 - Gradually add heat-treated flour and salt on low speed, mixing just until combined and no dry patches remain.
04 - Gently fold mini chocolate chips into frosting using rubber spatula until evenly distributed.
05 - Use immediately or refrigerate up to 3 days. If chilled, bring to room temperature and stir before application.