In a medium skillet over medium heat, melt butter. Add minced garlic and cook for 30 seconds until fragrant.
Pour in balsamic vinegar and stir, scraping up any browned bits from the bottom of the pan. Let cook for 2 minutes until slightly reduced.
Add beef broth, Worcestershire sauce, brown sugar, Dijon mustard, and black pepper. Stir well to combine and bring to a simmer.
In a small bowl, whisk together cornstarch and cold water until smooth. Pour into the sauce while stirring constantly.
Continue simmering for 5-7 minutes, stirring occasionally, until sauce has reduced by about half and is thick enough to coat the back of a spoon.
Remove from heat and stir in fresh parsley. Drizzle over cooked steak tips and serve immediately.