How to Make It
Combine mushrooms and flour in a bowl; toss well.
Combine wine, shallots, and vinegar in a medium skillet. Bring to a boil; cook until thick (about 3 minutes). Reduce heat to medium. Add broth, Worcestershire, tomato paste, and rosemary; cook 1 minute. Add mushroom mixture; cook 3 minutes, stirring constantly. Stir in mustard.