2 pounds of stewing beef, cut into 1 inch cubes. (I recommend beef chuck or short ribs cut off the bone. See notes below)
Freshly ground black pepper
2 tablespoons vegetable oil
10 ounces of white button mushrooms, thinly sliced
6 ounces of shiitakes mushroom caps thinly sliced
1 large yellow onion, peeled and chopped
2 stalks of celery, diced
6 large cloves of garlic, roughly chopped (2 tablespoons)
12–16 cups low salt chicken broth or homemade chicken stock
3 large carrots, peeled and sliced into 1/4-inch rounds
2 teaspoons dried thyme
2 bay leaves
1 cup toasted buckwheat groats, also called Kasha
1 1/2 pounds yellow flesh Idaho potatoes, peeled and diced
1 broccoli crown, cut into small florets
Season beef generously with salt and pepper. Heat oil over medium-high heat in a large heavy soup kettle or Dutch oven until very hot. Add half the beef and sauté, turning occasionally, until brown on all sides, about five minutes. Transfer to a plate and repeat with the rest of the beef cubes. Transfer to the plate and set aside.
Add mushrooms, onions and celery to the pot. Sauté vegetables, stirring occasionally, for 7-8 minutes, or until the water released by the mushrooms is evaporated and the vegetables just start to brown. Add garlic and cook, stirring, for one minute.
Return the beef to the pot. Pour in 12 cups of chicken broth, carrots, thyme, bay leaves,1 1/2 teaspoon of salt and 1/2 teaspoon of pepper. Bring to a boil. Lower to a simmer and cook, uncovered, for 1 hour and 45 minutes.
Add buckwheat and potatoes. Bring the soup back to a simmer and cook for 20 minutes longer.
Add broccoli and simmer for a final 5-10 minutes. If you want a thinner soup, add more chicken broth. Season, to taste, with salt and pepper. Ladle into bowls and serve hot.
If you decide to use short ribs, I found that 4 1/2 pounds of short ribs (6 meaty ribs) yields 2 pounds of meat. I suggest cutting the meat off the bones and cubing it up. When you add the broth in step #3, add as many bones as comfortably fit in the pot. I added 3 and froze the rest for future broths.