Preheat oven to 350°F. Use 1 tablespoon of the softened butter to grease the sides and bottom of a 1 1/2-quart baking dish. Set aside.
Combine the cubed pasteurized cheese, cubed cream cheese, and shredded cheddar cheese in a bowl. Toss. Set aside.
In a large bowl, gently toss the potatoes, chopped hardboiled eggs, crumbled bacon, green onion, and pimentos.
In a separate bowl, whisk the mayonnaise, sour cream, melted butter, apple cider vinegar, Worcestershire sauce, black pepper, and reserved bacon drippings. Pour over potato mixture and GENTLY toss to coat making sure to incorporate very well.
Spoon half the mixture into the prepared casserole dish. Top with half the cheeses. Repeat with the remaining potato mixture and the remaining cheeses. Top with the reserved bacon, reserved green onions, and the sweet paprika.
Bake for 20 to 25 minutes, or until thoroughly heated through and casserole is bubbling. Serve hot.