Boil potatoes a day ahead. Cover and refrigerate overnight.
When ready to cook, preheat oven to 350°F.
Cut cooked potatoes into quarters. Place in a large mixing bowl. Set aside.
Place butter and garlic in small saucepan. Place on stovetop and heat over medium heat until butter is completely melted. Pour hot garlic butter over potatoes in bowl.
Add 3 tablespoons Romano cheese.
Add milk, Monterey Jack cheese, Cheddar cheese, green onion, salt, black pepper, white pepper and paprika.
Mix ingredients thoroughly with your hands, gently squeezing through your fingers. Do not overmix - there still should be large chunks throughout the mixture.
Transfer mixture to a 13 x 9 x 2-inch casserole dish.
Sprinkle with remaining 1 tablespoon Romano.
Cover and place in preheated oven. Bake 35 minutes.
Remove from oven and serve immediately.