Suppengrün is the German version of the aromatic vegetables that form the base of many stews and braises (Mirepoix in French, Soffritto in Italian), which translates to "Soup Greens." This variation uses leek or onion, celery root (a.k.a. celeriac), and carrot. There are two ways to use suppengrün: to make a liquid base for a soup, boil large chunks of each for a few hours, and then discard the spent vegetables. Add some parsley and salt and you have a simple veggie stock. Or, if you're preparing a meat dish or a braise, prep first: peel the celeriac, use only the white and light-green parts of the leek, and discard carrot tops. Chop all three veggies into a small, 1/2" dice, and sauté in a fat (oil or butter), until aromatic.
Split Pea Soup is an easy, make-ahead dish that reheats well and is perfect for Fall.
Prepare your veggies: scrub and dice the carrots, peel and chop the onion or leeks, and then get to the celery root/celeriac bulb: first rinse the dirt off, remove the leaves (really flavorful for making stocks or minced in a salad, or stuffed under the skin of a roast chicken.) Then, attack it the same way you do kohlrabi-- slice off the root and tip, then using a sharp paring knife, remove the gnarly outer layer. The inside is softer and spongier, and smells like strong celery.
Melt butter in a 6-qt heavy-bottomed pot. Cook bacon until crisp, transfer to a plate lined with paper towel to drain. Add in suppengrün (onion, carrot, and celery root), reduce heat to medium-low, season with about 1 tsp of salt and cook until soft, about 10 min. Sift flour over veggies, and toast for an additional 3 minutes.
Meanwhile, make your bouquet garni: using either cheesecloth or kitchen twine, make a small bundle of your herbs.
Into the pot add the split peas, the ham hocks and the 7 cups of warm stock or water. Add in the bouquet garni, another teaspoon of salt, and bring to a boil over high heat. Once boiling, reduce the heat to a simmer, and cook until the peas are tender (1 hour.) *This can also be done in a slow-cooker: 4-5 hours on high or 6-8 hours on low.
Remove the pot from the heat, and discard the spent herb bundle. Transfer the hock to a separate plate or carving board, and let cool for a few minutes. Use an immersion blender to blend soup to desired consistency-- I like to take out about half of the soup and only puree the half still in the pot, then add back in the textured soup. Once the ham hocks are cool enough to handle, chop up the meat and discard the fat, skin and bones. Add the meat back to the soup, taste to adjust seasoning, and serve with reserved bacon sprinkled over top.