Add the dried peas to a large bowl and cover with cold water by two inches. Add 1/2 tablespoon kosher salt and soak overnight. Drain then rinse the peas before proceeding.
If you can't soak overnight, add the peas to a pot, cover with water (no salt) and bring to a boil then turn off and let the peas sit for one hour before continuing. Drain this liquid before proceeding.
Fill a large pot with chicken stock or water, add just the ham hock and simmer for 30 minutes to soften it, then add the peas, celery, diced onion and garlic.
Reduce heat to medium low, cover and simmer gently until the peas are soft; about 2 1/2 to 3 hours.
Remove the hock, peel away the tough outer skin and shred the ham that's left. Add the ham back to the pot.
If you're using chopped collard greens, stem and dice them roughly then add them to the warm peas to simmer for 5 to 10 minutes until soft. Serve warm. Refrigerate any cooled leftovers for up to five days.