How to recook a roast? I bought a chunk of vacuum packed beef from the discounter. The label said "roast meat", and didn't indicate which cut of beef it was. It was lean meat (4% fat), but that's normal in Europe. 

I roasted the meat with some glaze, at 175°C, until the probe showed 63°C. Then I seared the crust on a 320°C iron pan. It turned out somewhat rare (I suspect the probe isn't good enough), but still looked like a perfectly good roast. But when I started eating, I discovered that the meat has enough connective tissue to be practically unchewable in this state. 

Now I want to recook the meat and eat it. My first idea was to make goulash, in chat I got the advice to make a stew. The point is, while I know that theoretically it should work, I've never recooked meat, and I don't know if there are some details I'm overlooking. Also, is there a special kind of stew particularly well suited to my case?

Is there something special about making a stew or a goulash with precooked meat, different from using raw meat? Am I forgetting something here? How long should I cook the meat? (Assume that I start measuring after the center of the meat pieces - whatever size - has reached 68°C). I have roughly 20% to 25% connective tissue, the thickest fascia are maybe 3 mm. The meat is already roasted, seared, rested and cooled (and will be refrigerated when I start recooking). 

You don't have to explain the food safety implications, I am aware of them. Just assume that in this case, I am willing to take the risk of eating the recooked meat. 

Edit I am not all that interested in recipe suggestions, I guess a common stew will do. What I want is to know how the usual technique of slow cooking changes when the meat is precooked, and if somebody has already done this and can confirm that it works. By the way, the meat is now cut in chunks and marinating in the fridge.
Stewing tough or thoroughly connective-tissued meats is, by design, something you do for a long time at pretty decent temperatures. Since your meat has already been cooked once, if anything you are going to be cooking it slightly less than what is described in whatever stew you decide on. Your food safety concern is admirable, but as long as you observe good food handling safety and cook the meat thoroughly, you should be good to go.

I will reiterate the chat's suggestion for a stew as a good one. However, a stroganoff (which is an American version of an Eastern European dish, I believe) would also be a good option. Basically any beef dish where the beef is diced up evenly in size and stewed in a sauce for a long while will work in helping you to use up this meat.