Any cut of beef will work for stew. It used to be (back in the dark ages when I was a young wife just starting out) that "stew beef" was the throw-away meat left over from the other, more expensive cuts. You could get it for next to nothing, and it had lots of fat in it. Times have changed, however, and now "stew beef" is considered a cut of it's own and they charge premium prices for it. Don't let them fool you, and don't pay expensive prices for throw-away odds and ends of meat. Buy a cheap cut. It doesn't matter how tough, because the stewing for hours will soften up the toughest meat.
And that half an onion behind it is the next thing you'll need.
This is called a mandolin, not to be confused with this one:
One is an instrument you play with your fingers, the other one will take your fingers off in a red hot second if you use it carelessly!
If you have one of these (and use it right) it will slice up that onion in a matter of seconds. If you don't have one, you can do it the old fashioned way, it's not a requirement, just a way to make your job quicker.
You don't have to do this step, either, if you're in a hurry. It just seals in the juices and keeps the flavor in the meat a little bit better than if you skip the browning.
That crispy dark brown on the edges is what you're looking for. That's the best, tasty part!
Toss them from the frying pan into the slow cooker.
This is the part where you add your seasonings. Mix the Au Jus with water till the lumps are gone. Pour over your meat and onions.
Toss in a tablespoon or so of minced garlic, and a heavy sprinkling of ground sage, and maybe a little bit of pepper. You won't need a lot of salt, because it's already in the Au Jus.
Turn your crock pot on high and walk away. That's all there is to do for the next three or four hours. You can turn it on low and leave it for six to eight hours if you're going to be away from home.
About two hours before you want to eat, cut up four or five red potatos (regular spuds will work just fine, too) and a handful of baby carrots (one or two regular will do, too). Again, this amount will depend on how much your crock pot holds.
Here's a note for you: Carrots will cook faster and more evenly if you split them down the center lengthwise so the heart is exposed. Cut them in half, then cut into bit size sizes.
Your pot will have cooked down, and the water will be way too low when you add the vegies, so top off the pot with warm water.
Put the lid back on and leave on high for at least two hours.
You can also add other things, like a can of corn or a handful or barley right now, if you'd like.
A few minutes before you want to serve it, mix a tablespoonful of corn starch with a half cup of hot water. Mix till it's smooth and liquid, then pour in. That will thicken it up to make it stew instead of just soup.
Serve with crackers, or with bread and butter. It will warm your tummy up better than anything else on a cold winter evening!