In a large pot, cook bacon until crisp and fat is rendered. Transfer to paper towel to drain. Reserve about a tablespoon or so of fat in the pot.
Add onion, carrot and leeks to pot. Sprinkle with some salt and cook until vegetables have softened and lightly browned, about 5-10 minutes.
Stir in bay leaves and thyme, and then add the split peas and lentils, celery and reserved bacon. Cover with the chicken stock. Add the shredded potato and ham hock, season with more salt and some pepper, and bring to a boil. Turn down to a simmer, cover with lid slightly askew.
Skim any foam that rises to the surface during the first 10-15 minutes. Stir occasionally and simmer for another 45 minutes or until the split peas and lentils are tender. Add more stock if the soup seems too thick.
Remove ham shanks, cool slightly and cut up meat and add back to the soup.
Check for seasoning and serve.