Baked Mashed Potatoes with Parmesan & Bread Crumbs

1 tbsp butter
4 pounds russet potatoes (about 10 medium), peeled and cut into 1 inch pieces
1/2 cup butter, melted
1 cup whole milk
1.5 cups grated mozzarella
1 cup freshly grated parmesan
salt and pepper
2 tbsps plain dry bread crumbs

Preheat oven to 400, coat a 13x9x2 inch baking dish with 1 tbsp butter and set asideCook potatoes in large pot of salted water until they are very tender, about 15 min. Drain, return potatoes to same pot and mash well. Mix in milk and melted butter. Mix in the mozzarella and 3/4 cup of parmesan and season to taste with salt and pepper. Transfer potatoes to prepared baking dish. Stir the bread crumbs and remaining 1/4 cup of parmesan in a small bowl to blend. Sprinkle the bread crumb mixture over the potatoes and bake, uncovered until the topping is golden brown, about 20 minutes!