Saw another post and those who commented were right...

BOTH should be stored in cool, dark places. and not with each other (just keep with a bag or something between them. 

ONIONS---chop and freeze to cook with.    Peel and half one and keep in plastic keeper in fridge.  Is very easy to grab and chopp just a smidge here and there for our individual servings if we have picky eaters who whine or can't take it.  (This way WE are not deprived of the great flavor)  Also don't buy too many if you can't use them fast.  You don't want them to sprout.

POTATOES---When storing them, you should put a bag or towel over them if they are exposed to light. (Otherwise, they will turn green. They could still be peeled and edible then, but for anyone with compromised immune system... like elderly, those with chronic illness...they CAN BE TOXIC.) If they would start with eyes, I have already just plucked the little suckers off and proceeded. I have friends who do love to experiment and have actually used these to start their own plants. I am not that ambitious. lol

Always wash or scrub them. If you want to save time, you can peel and prep them for use later just cover them with cold water and store in fridge. Then when you start cooking, you are good to go. 

PS You can do unpeeled garlic mashed potatoes. throw in 2 peeled cloves of garlic with washed, chunked unpeled potatoes (reds are excellent) Drain and mash... add a smidge of  milk, butter and seasoning.  MMMM

for those who are lactose free--- mash with a small bit of the liquid undrained.   And for extra creamy, use evaporated milk.   Both are tasty options.

HOME FRIES--- when frying raw potatoes, sometimes they brown too fast and are not getting tender fast enough. I add a bit of water and cover. As that cooks off, they will again continue to fry. 

SPUDNIKS--- My Aunt used to make yummy fries and called them this.  She would partially bake potatoes , then cut into a few large thick fries (4-8 depending how big the potato and how big you wanted them)  In a bowl mix some flour, salt, pepper, paprika, and dash of cayenne if you want a little kick.  Dump this into a large sealable baggy..   Lightly coat the potatoes in oil, then the flour mixture.    Fry them  (deep fry or pan with oil) The cooking time is cut in half since they are almost ooked before you start.

Crunch with tender tater in the middle... YUM.   (can also use garlic salt and grated parmesan for cheesy garlic ones)