In a small bowl, combine vinegar, brown sugar, mustard, garlic salt, and pepper. Whisk until sugar is dissolved. Slowly whisk in oil. Cover, and refrigerate until ready to serve. Store in an airtight container for up to 2 weeks.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/summer-garden-salad-balsamic-vinaigrette-recipe/