Preheat your oven to 350F
Put your stove to oven safe dutch oven or heavy bottom pot on medium heat.
If the meat is really wet, pat dry with a paper towel. Season with salt and pepper.
Add oil or butter to your pan and Brown the meat in batches, putting browned meat onto a plate or bowl to wait for you.
When all the meat is browned, saute the onions until they're a little browned.
Add in garlic, give a stir and then add in your broth and wine, stir, scraping the bottom, to get all those good browned bits!
Add back in your meat, as well as mushrooms, tomato paste, worchestshire, mustard, salt and pepper.
Put the lid on and tuck into the oven for 1 hour.
After an hour, take it out, stir it around, and gauge if it needs more. Depending on your meat, it may need another 30 minutes. You want it to easily pull apart with a fork. Depending on your pot, it may trap or let out a lot of moisture, so add a bit of water in if you think it doesnt look very saucy.
If you're going to eat it all right now, add in all the sour cream. If you plan to freeze some, take out half for freezing, add half the sour cream to the instant pot and stir it around.
Taste for salt and pepper, serve on top of mashed potatoes or buttered egg noodles.
Keeps 3-4 days in fridge, or freeze without sour cream and when ready to eat, thaw, simmer and add in sour cream before serving.