Slice peeled (or well washed) potatoes into thin but large slices.
Peal and thinly slice the onion.
Mix cheddar cheese soup with 2/3 (soup can) of milk (you may also add finely chopped garlic).
Pour into medium size roasting pan.
Begin to layer potatoes (after every two layers, add onion to taste as well as salt, pepper, and other spices like parsley).
When pan is approx. half full, add mushroom soup (mixed with milk).
continue to layer potatoes (onion, and spices).
Bake for approx. 1:30hrs for 350-375 (depending on how hot your oven is).
Remove from oven, place cheese on top, adjust temp. to 300 and continue to bake uncovered for 20mins or cheese is bubbily.