Cheddar and Chive Mashed Potatoes

ngredients

• 5 pounds Yukon Gold potatoes, peeled and cut into 1-inch pieces (about 10 cups)
• 1 cup butter, cubed
• 1 cup sour cream
• 2 teaspoons salt
• 3/4 teaspoon pepper
• 1/2 cup heavy whipping cream
• 1-1/2 cups shredded cheddar cheese
• 1-1/2 cups shredded Monterey Jack cheese
• 1/4 cup grated Parmesan cheese
• 2 tablespoons minced fresh chives
• toppings:
• 1 cup shredded cheddar cheese
• 1 can (6 ounces) french-fried onions