1. Preheat oven to 425 degrees Fahrenheit. Combine brown sugar, mustard, soy sauce, and vinegar in a small pot. Bring to a boil. Remove from heat.
2. Place ﬁllets on foil-lined pan, greased with oil or cooking spray. Sprinkle ﬁsh with salt and pepper. Bake at 425 degrees Fahrenheit for 12 minutes. Remove from oven.
3. Preheat broiler. Brush sugar mixture evenly over ﬁllets. Broil for three minutes or until ﬁsh ﬂakes easily with fork.