HEAT oven to 400°F.
SPRAY foil-covered rimmed baking sheet with cooking spray. Add 1 tsp. basil to coating mix in the shaker bag; shake gently to combine. Use to coat fish as directed on package. Place in prepared pan.
BAKE 20 min. or until fish flakes easily with fork. Meanwhile, cook potatoes in boiling water in large saucepan 15 to 20 min. or until tender.
DRAIN potatoes; return to pan. Add milk, grated topping, reduced-fat cream cheese, rosemary and remaining basil; mash until mixture is blended and of desired consistency. Serve with fish.