Recipe: Smashed Potato Casserole

Name: Recipe: Smashed Potato Casserole
Ingredients: 3 pounds russet potatoes, peeled and cubed; 1 cup (8 ounces) sour cream or plain Greek yogurt; 1 cup whole or 2% milk, plus more as needed; 8 ounces sharp cheddar cheese, grated (about 2 1/2 cups); 2 medium shallots, minced (about 1/2 cup); 2 teaspoons kosher salt; 1/2 teaspoon freshly ground black pepper; 1/2 cup grated Parmesan cheese