Cook potatoes in a large pot of boiling water until tender.
Mash until there are no lumps.
Add cream cheese, sour cream, onion powder, salt, pepper, and egg whites; blend well.
Cool slightly, place in removable liner of your crock pot and place in the refrigerator.
Take out of refrigerator about 3 1/2 hours before you plan to serve it.
Place in crock pot and dot with butter.
Cook on LOW for 3 hrs., stirring once or twice.
They can be held an additional 30 minutes or more.
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