Heat a large pot over medium high heat and add the olive oil.
Pat the cubes of beef dry and season them with salt and pepper.
Brown the beef on all sides in the pot (in batches if necessary - do not overcrowd the pot!), and remove the beef to a plate once each side is browned. Don't worry about cooking the beef all the way through at this stage.
Once the beef has been removed to a plate, add the carrots, celery, onions, garlic and thyme and saute until the onion is translucent and the veggies are soft.
Add the wine and stir to deglaze the bottom of the pot, until the wine has reduced.
Add the beef stock, cooked barley, and add the beef back into the pot.
If using uncooked barley, add 1/2 cup uncooked barley and increase the amount of stock to 5 cups. This will yield a creamier (less broth-y) soup.
Stir well to combine and cover. Reduce the heat to medium low and cook for about 30-35 minutes, stirring every 15 minutes or so.
Add the kale, stir well and cook for 5 more minutes, covered.
Serve with crusty bread.
To use uncooked barley, add 1/2 cup uncooked barley and increase the amount of beef stock to 5 cups.