Cut pork roast into 1 ½" cubes removing any thick fat veins.
Toss pork in a bag with ¼ cup flour, 1 teaspoon salt and 1 teaspoon paprika to coat uniformly.
Heat the oil in a large skillet and brown the pork in one layer. Work in batches if necessary.
Add onion and garlic to a slow cooker.
Combine broth, wine, tomato paste, thyme and remaining salt and paprika in a cup. Add pork to the slow cooker. Pour broth mixture into the skillet and scrape up any brown bits. Stir to mix evenly and pour over the pork in the slow cooker.
Cook on high 3 hours. Add the mushrooms and the sour cream and cook 1 hour more.
After the 4th hour, check the seasonings and adjust if necessary. If you want the sauce to be thicker remove a cup of broth and dissolve 1 tablespoon of flour in the hot broth. Microwave 1 minute and stir. Repeat until the sauce has thickened and then add back into the slow cooker. Mix well.
Serve over egg noodles, rice or spatzle. Garnish with parsley if desired.