Cut onion in half, char on the bottom of a stock pot, no oil or butter needed.
Add 48oz of beef broth and 6 cups of water to the stock pot over high heat. Feel free to adjust the broth to water ratio depending on how “meaty” you would like your stock.
Once the liquid is boiling, add beef bones, beef, salt, and peppercorns. Boil for 1-2 hours. Skim foam as necessary. Adding the bones first helps to keep the meat off the bottom of the pot and possibly burning.
Towards the end of the 1-2 hours, peel carrots and parsnips, slice on the bias. Peel celery root and cut into 1 inch cubes. Cut the leek in half lengthwise and wash thoroughly. (Leeks can have sandy soil trapped between their leaves). Slice your now clean leek halves.
Once the beef has boiled for 1-2 hours add your cut-up carrots, parsnips, leek, and celery root.
Boil for 30 minutes to 1 hour; depending on how firm you prefer your vegetables. Longer = more flavor in the stock but a mushier feel to the vegetables.
While your meat and veg is cooking, grate your potatoes. Added the grated potatoes to a well-oiled pan and sauté until browned on both sides.
Grate the apple and mix with the horseradish. Juice the lemon juice, add to the apple & horseradish, and set aside. (This is a traditional side; but if you don’t like it feel free to simply use horseradish sauce mixed with a bit of sour cream)
Remove meat from the pot, and cover with foil. Pour contents of pot into a colander or sieve with another pot sitting below the colander/sieve to catch all the clear broth. DON’T DUMP ALL THAT GREAT BROTH DOWN THE DRAIN! Transfer strained broth to the large pot.
Set carrots, parsnip, celery root, and celery root aside.
Gently reheat broth. Add salt 1tbs salt (or more) to taste.
Toast sliced bread. Top with bone marrow.
Thinly slice 1 bunch of chives.
Once the meat has rested for at least 5 minutes, slice 1/2-inch thick across the grain. Place in soup plates/bowl. Add carrots, parsnips, and celery root; moisten everything with a good amount of hot broth. Top with apple-horseradish and/or sour cream/horseradish, and/or hash browns. Add salt and pepper to taste. Top with chives.