Rich Potatoes Gratin

5 lbs. potatoes; peeled and sliced
2 c. whipping cream
4 oz. cream cheese
1 1/2 c. cheddar cheese
1/2 c. dry breadcrumbs
1 1/2 dried rosemary, crumbled
1/4 c. butter, cut into small pieces

Preheat oven to 425 F (220 C). Butter 15 x 10 inch (38 x 25 cm) glass baking dish. Layer potatoes in prepared dish, sprinkling each layer with salt and pepper. Bring cream to boil in heavy medium saucepan. Reduce heat to medium. Add cheesees to cream; whisk until cheese melts. Pour cream mixture over potatoes. Cover with foil. Bake until potatoes are tender, about 1 hour.

Preheat broiler. Mix breadcrumbs and rosemary in small bowl. Sprinkle over potatoes. Dot with butter. Broil until butter melts and crumb mixture is golden brown, watching closely; about 4 minutes. Let stand 10 minutes.