In small bowl, combine tomato sauce, brown sugar and mustard; set aside.
In large bowl, combine remaining ingredients. Add 1/4 cup reserved sauce mixture to meat mixture and incorporate. Divide meat mixture evenly and place into prepared muffin cups. Place muffin pan on baking sheet.
Bake 25 minutes or until no longer pink in centers (165 F).
Top each mini loaf with 2 tablespoons sauce; bake 5 minutes more or until sauce is set. Serve with remaining sauce.