I've never put cream cheese in mashed potatoes*, and never frozen cooked potatoes, except maybe as part of a stew. Recipe please?
*My favourite mashed potatoes are potatoes cooked with whole cloves of garlic, drained, lightly mashed, a bit of cream and butter added plus salt and pepper, and then mashed a bit more. I like them on the dry side, still with little chunks. My MiL used to whip them with a lot of milk and they were so soft and squishy. I know lots of people prefer them that way. They were very good for making a depression in the middle to hold gravy.
My preference is probably for mashed potatoes made with butter and cream, but I do really like the cream cheese mashed potatoes. They are drier/thicker than the "whipped" kind of mashed potatoes. As a side note, I grew up with mashed potatoes being made with margarine and 2% milk, and never knew really great mashed potatoes until I was an adult.
The make ahead recipe comes from the book "The Freezer Cooking Manual from 30 Day Gourmet : A Month of Meals Made Easy". When you defrost the potatoes they will absolutely look like they aren't going to be good, but they do reheat beautifully. I often just use the microwave to heat them, or a pan, but the original recipe calls for freezing them in casserole dishes and reheating in the oven.
The recipe is given for various numbers of servings: 7 C., 14 C., 21 C., 28 C., 35 C., and 42C. I will give the recipe for 14 C., because you can double it for 28 C. and triple it for 42C, or half it for 7 C. These days I just do 5# of potatoes.
Make Ahead Mashed Potatoes
10 lbs. potatoes
2 eggs
1 t. garlic powder
2 t. salt
16 oz. cream cheese
Peel and quarter potatoes. Place in saucepan, completely cover with water. Bring to a boil and gently cook until tender. Drain well. In a large bowl combine potatoes, cream cheese, eggs, garlic powder and salt. Mash well by hand or with an electric mixer. Spoon potatoes into spray treated casseroles dishes (use whatever size you need). You can also freeze in Ziploc freezer bags or containers.
(The recipe also calls for topping the potatoes with melted butter and sliced almonds, plus paprika for color. I skip all of that.)
To serve, thaw completely and bake at 375 degrees for 30-40 minutes or until top is golden. If you want them last minute, defrost them in the microwave, then increase power and heat through.
Here is the recipe written out for 5# potatoes and cooked in the Instant Pot:
Make Ahead Mashed Potatoes, Adapted for Instant Pot
from The Freezer Cooking Manual from 30-Day Gourmet: A Month of Meals Made Easy by Tara Wohlenhaus and Nanci Slagle
Make Ahead Mashed Potatoes
5# potatoes
1.5 C. water
1/2 t. garlic powder
2 t. salt
8 oz. cream cheese
1 egg
Scrub potatoes well, the cut into large chunks (peel if you want)
Place into Instant Pot inner pot along with 1.5 C. water.
Place lid, check for sealing, and pressure cook for 10 minutes
Do a quick release of pressure (can allow to come down naturally)
Drain any remaining water
Add cream cheese, garlic powder, and salt
Use a hand mixer to mash potatoes
When partially mashed, add in egg and finish mixing until smooth
Taste for seasoning and add more if desired
For storage, spoon mashed potatoes into buttered oven/freezer safe storage container. Cover and allow to cool completely in refrigerator before transferring to freezer.
To serve, thaw completely, remove cover if plastic, and bake at 375°F for 30-40 minutes or until top is golden. Or you can defrost them in the microwave, then increase power and heat through.