Mom's Scalloped Potatoes

Mom actually got this recipe from someone named Lorene Eldridge. no clue who she is. This dish was only served at the holidays -- Easter and Xmas. not sure why, but it was always a nice treat.

[edit: figured out why they're "special occasion only" -- they take for freaking EVER to make! 45 minutes to boil the potatoes, time to cool, peel and shred, and then the endless stirring to melt the cheese, and an hour to bake. *collapses*]

8 large potatoes
1 cup milk
1/4 lb grated cheddar cheese
1/4 lb grated mild cheese
1/2 pint whipping cream* (not whipped!)
1 tsp mustard
pepper to taste
1/2 cup chopped onion

Boil potatoes with jackets on. cool, peel and grate into baking dish. heat other ingredients together until cheese melts. pour over potatoes. sprinkle with paprika. bake one hour at 325.

Can be made ahead and refrigerated

* i have trouble finding whipping cream at the holidays, so i just use 2 cups half-and-half for the milk and cream.