I have been trying to sauté beef and make pan sauces, but the meat seems to always become somewhat dry and chewy. How do I avoid this? I have the same issue when stewing beef in a slow cooker or dutch oven.
The cut is important for both techniques. For sauteing, you need a lean cut - fillet, sirloin, or good rump steak. These should be cooked quickly over a high heat. As Cerberus has suggested, if you are cooking something else in the same pan, take the beef out and re-add it later; don't boil it in a sauce.
Stewing beef needs some fat and cartilage which breaks down during slow cooking and tenderises the meat. Packs of such beef are usually sold as such in the supermarket; look for a pack with plenty of fat marbled through the meat; 'Lean stewing steak' is as useful as a waterproof teabag! My personal favourite stewing beef is brisket, as it breaks down into nice tender fibres after 2-3 hours cooking.
Contrary to popular belief, browning meat does nothing to 'seal in the juices'. It simply provides a bit of extra colour and flavour by 'caramelising' the outside a little. So if you have a strong flavoured stew (like a chilli, for example), just throw the chunks of meat straight into the sauce.
I'd say you either sauté it on a very hot fire (in oil/butter, no watery liquids yet) for a very short time (less than a minute if you have small chunks), or you let it simmer for as long as possible, so that you get a stew-like effect, which makes it tender in a very different way, could be 45 to 180 minutes for a real beef stew. Anything in between usually doesn't work for me.
I sometimes put the beef in a bowl after sautéing, then add it back into the pan when the sauce is ready to be served. You could put the bowl in your oven at low temperature (60–100 C, 150–220 F?) to keep it a bit warm while you make the sauce. Just as you can keep a steak warm at ca. 150 C for ca. 10 minutes after frying it for a few minutes (works well for me). Or you could just sauté the meat in a different pan just before serving it.
I think bmike has hit it on the head. If you're cooking with a well marbled good cut of beef then cooking it too much will toughen it. If you've a lesser quality cut of meat then long braising will render it tender... the falling apart on your fork effect.
When I am making beef stew I figure I'll be simmering it for a fairly long period of time, so I buy packaged stew beef, mostly because of the cost factor, brown them well, and then add them to the dish.
This is similar to buying a lesser quality roast that you'll put in the oven or braise for a long slow low temp period of time whereas I'll cook my 1 1/4" rib steak for 6 or 7 min on the highest heat to maintain tenderness.
When frying: Try using a less lean cut, or if you want to use a lean cut try marinating it in oil for a while beforehand. The fat; either natural in the beef, or oil from the marinade; will help you against dry and chewy.
When slow cooking: If you sauté before slow cooking it is unusual to get dry and chewy, even with the worst cuts. Maybe your slow cooker does not get hot enough or you don't cook for long enough. Slow cooking often takes hours.
It's a bit odd, but tenderness is something you cook out of very tender meat. So, keep the temperature as high as you can and the cooking time as short as possible based on the thickness of the meat.
If you start with a tough cut or have cooked the tenderness out of a steak, then it's a long slow process with hours of moist cooking in a crock pot to break down the fibers and return the meat to a tender place.
I'm a Cajun so I cook slightly different. I have never had a problem with my stew meat and I use everything from Walmart to whole foods. The key for me is when I marinate it, even if for 20 minutes, I use pineapple juice. This breaks down the amino acids. This can also be done with wild game. Not to worry your food will not have a pineapple taste. Monitor your meat if your doing the low and slow option after about and hour go test your meat if it seems a little chewy cook for another 30 then you will be fine.
Hope this helps.
I found if you wish to tenderize cheap tough meat, gravy beef before you cube it, lay first layer in bowl, cover in lots of salt, place next layer and so on till all is covered. Then leave for an hour, pull out meat and thoroughly rinse off all salt. Cube it and crock pot the stuff in a thick gravy sauce. You will be pleasantly surprised how tender cheap cuts can be good for BBQ as well.