Preheat the oven to 350ºF (see notes below for stove top preparation). Before the oven gets hot, adjust the oven racks so that your soup pot will sit centered within the oven (e.g., sometimes I have to remove the upper rack so the lidded pot will fit, with the second rack on the 2nd from bottom notch).

In a large 5 to 6 quarter soup pot or Dutch oven, heat the oil over medium. When the surface of the oil shimmers, add a portion of the beef and bacon, to cover the bottom of the pot in a single layer. You'll have to work in batches. Brown the beef on all sides, letting the bacon fat render into the pot. When the beef has seared edges, transfer everything to a bowl, and repeat with the next batch. (Time-saving tip: I also use a large skillet on another burner, which is roomy enough to hold the remaining beef, and can brown everything simultaneously. It's an extra pan to wash, but it saves so much prep time.)

There will be some beef drippings and bacon fat in the pot, but if it's not sufficiently covering the surface of the pot, pour in a little more oil.

Add the onions, celery, carrots, parsnips, and mushrooms. Stir well and saute until softened, about 5 minutes.

Remove about two-thirds of the cooked vegetables to a separate bowl and set aside. The vegetables left in the pot will flavor the soup, while the reserved vegetables will be added later, so they don't soften to mush.

Spoon the tomato paste, smoked paprika, and garlic into the soup pot, and stir well. The garlic should quickly become fragrant.

Return the beef and bacon to the soup pot, along with any juices from their bowl.

Pour in 4 cups of beef broth, and lay in the thyme sprigs and bay leaves. (Reserve the remaining broth.)

Cover the pot with a lid and place in the oven. Start the timer: from here, the soup will cook for about 90 minutes.

At the 45 minute mark, remove the pot from the oven and stir in the barley and Worcestershire sauce. If the thyme sprigs are bare of leaves and are sticking out, in your way, you can go ahead and remove them.

Replace the lid, and return the pot to the oven for the last half of the cook.

Check the soup after 30 minutes. If the pearled barley is fresh (in the sense of not old and stale), it could be finished cooking in 30 minutes. Barley is done when it's got some puff to it and is slightly sturdier than brown rice. More likely, it will need 45 minutes (possibly 60 minutes if on the older side).

If any point, the soup is getting too chunky and stewy for your liking, add part or all of the remaining broth. Replace the lid and return the soup to the oven.

Add the reserved vegetables in the final 15 minutes of cooking.

Test a piece of the beef: it should be very tender and easy to chew.

Fish out the bay leaves and thyme stems (the leaves have probably fallen off into the soup - this is good. Just discard the woody stems.) Give everything a good stir and taste. Add salt as desired.