Thoroughly wash, peel, and cut your potatoes into roughly 1 inch cubes. Remove any bruised areas.
Place the potatoes in a large pot and cover with cool water.
Heat over high heat and bring the water to a boil, allowing it to boil for about 30 minutes or until fork tender.
Remove from heat and drain the water into a colander.
Return the potatoes to the pot or a large bowl.
Add in the butter, half of the cream, and cream cheese and mash the potatoes with a potato masher.
Mix until the potatoes start to mash with some lumps.
Add in the cheddar and parm cheese and continue to mash until mostly smooth.
You may still have some lumps when done. For smoother mashed potatoes, use a hand blender.
After you fully mix in the cheeses, check the potatoes for moisture. If they are too dry, add a small amount of the remaining cream and mix to combine.
Check again and if it is still not moist, keep adding and mixing until you reach your desired level of moisture.