Wash, remove center stems and roughly chop or tear greens. Put in a large pot with the onions, celery, pepper and garlic and the water. Bring to a boil, reduce heat and simmer for 30 minutes. Drain greens, reserving cooking liquid.
Return cooking liquid to pot and add diced meats. Bring to a boil, reduce heat and simmer for 30 minutes. Drain meats, reserving cooking liquid.
Puree greens in a food processor. Add flour and stir through well.
Return greens puree, meats and enough liquid to make a soup to the pot. Season with thyme, salt and pepper. Bring to a low boil, then simmer for 45 minutes, adding liquid to keep volume and consistency and stirring occasionally.
Remove from heat and stir in file powder, and adjust salt and pepper. Serve over white rice or with french bread.