Peel and cut the potatoes into uniform chunks for even cooking.
Add the potatoes to the Instant Pot with 1 cup of water, then seal the lid securely.
Set the Instant Pot to high pressure and cook for 8 minutes until potatoes are tender when pierced with a fork.
Quick-release the steam carefully, then drain any excess water and transfer the potatoes to a mixing bowl.
Use a fork or potato masher to gently mash the potatoes until smooth but still slightly chunky for texture.
Stir in mayonnaise, vinegar, salt, pepper, and paprika until the mixture is creamy and well combined.
Spread the mashed potato mixture into a greased oven-safe dish or pie plate, smoothing the top with a spatula.
Sprinkle the grated cheese evenly over the top, creating a layer that will melt and brown in the oven.
Place the dish under a broiler or in a hot oven at 400°F (200°C) and cook for 5–7 minutes until the cheese is bubbly and golden brown.
Remove from oven and let it rest for a minute, allowing the crispy top to set slightly.
Serve hot, with a crispy cheesy crust on top and creamy mashed potatoes inside, perfect for a comforting yet quick meal.