Step 1In a 6-quart heavy-bottomed pot, combine the onion, carrots, celery, cabbage, garlic, oregano and vegetable broth. Bring to a boil over high heat, then reduce the heat, loosely cover and simmer until the vegetables are tender, 45 minutes to an hour.
Step 2Stir in the split peas and bring back to a simmer. Cover loosely and continue to cook, stirring occasionally, until the peas have softened and started to break down, about 1 1/2 hours, thickening the soup. Add additional water if needed to thin the soup (we added 2 additional cups after 1 hour). This makes about 3 quarts of soup.
Step 3Season with the salt, white pepper and Worcestershire sauce, and let the soup simmer for a few more minutes to marry the flavors. Taste and season again as desired.