Mashed Potato Layer Bake

4 large white potatoes, peeled, chopped and cooked
2 large sweet potatoes, peeled, chopped and cooked
1 tub (8 oz.) PHILADELPHIA Chive & Onion Cream Cheese Spread, divided
1/2 cup BREAKSTONE’S or KNUDSEN Sour Cream, divided
1/4 tsp. each salt and black pepper
1/4 cup KRAFT Shredded or 100% Grated Parmesan Cheese, divided
1/4 cup KRAFT Shredded Cheddar Cheese, divided

PREHEAT oven to 375°F. Place potatoes in separate bowls. Add half each of the cream cheese and sour cream to each bowl; season with salt and pepper. Mash with potato masher or fork until creamy.
STIR half of the Parmesan cheese into white potatoes. Stir half of the cheddar cheese into sweet potatoes. Alternately layer half each of the white potato and sweet potato mixture in 2-qt. clear glass casserole. Repeat layers.
BAKE 15 min. Sprinkle with remaining cheeses; bake 5 more min. or until cheeses are melted.