In a stock pot, heat olive oil to medium heat. Add onion, carrot, and celery to pot with 1/4 teaspoon salt. Cook for 8-10 minutes until vegetables are softened and onions are translucent. Add garlic and split peas, and cook for 1 more minute.

Add chicken stock, bay leaves, thyme, and black pepper to the pot. Add ham shank. Bring soup to a boil, stir thoroughly then turn heat down to a simmer and cover.

Simmer, stirring occasionally. After 45 minutes of cooking, remove ham shank so that you can let lightly cool, then shred meat off the bone. Add meat to pot (if you are using diced ham, add it now), then simmer soup for another 10-15 minutes, until split peas have started to break apart, are very soft, and desired thickness of your soup has been reached, adding 1/2 to 1 cup water. When desired thickness is achieved, discard thyme sprigs and bay leaves. Stir in vinegar and Worcestershire sauce. Taste and adjust salt by 1/4 teaspoon increments if needed.

Serve with crusty bread or croutons!

Leftovers keep well in covered container in refrigerator for 4 days. When reheating, add water to loosen.