1. Mix broth with cooked chicken.
2. Butter 2-quart shallow baking dish.
3. Mince garlic and place in small bowl.
4. Add to garlic, sour cream, 1/4 cup milk, onion, and mustard; stir.
5. Sprinkle potatoes with salt and pepper.
6. In prepared baking dish, place 1/3 of the potatoes; top with half of the chicken and broccoli and half of the sour cream mixture.
7. Repeat layer and then top with potatoes.
8. Pour remaining 1/2 cup of milk all over; sprinkle with lemon juice and Romano cheese.
9. Mix together margarine and bread crumbs; spread all over.
10. Bake in 375°F.
11. oven about 1 hour or until potatoes are tender.