Add the onion, beef, garlic, salt, pepper, paprika, cayenne, broth, and tomato paste to your slow cooker pan.
Gently mix everything together.
Cover, and cook on HIGH for 3 hours. You can also cook on LOW for 7 hours.
When done, whisk the cornstarch with water until smooth. Stir the slurry into the beef mixture. If you cooked the goulash on high, the stew should thicken immediately. If you cooked it on low, or if it doesn't thicken right away, set the slow cooker to high, cover, and cook for 15-30 more minutes, until the stew thickens.
Video
Notes
The nutrition info assumes that the meat has been trimmed of separable fat.This recipe was written for 2 lb. of meat. If your chuck roast is larger, say, 3 lb., you'll probably need to cook the stew for 4 hours on HIGH (8 hours on LOW). You should also add more seasonings and liquids - I would try adding an extra tablespoon of paprika and an extra half a cup of broth.As with most stews, the leftovers are wonderful. They keep well in the fridge, in an airtight container, for up to 4 days. I reheat them very gently, in the microwave, covered, at 50% power, to avoid drying out the tasty meat.