In a large pot over medium heat cook the onions, celery and carrots in the butter for 2 minutes.
Add the flour and mix well to coat the vegetables and make a roux.
Immediately pour in 500 ml of poultry stock and the milk and stir well to dissolve the roux.
Add the potatoes, thyme, bay leaf, salt and pepper. Bring to a boil while stirring and reduce heat to a simmer.
Simmer stirring occasionally to keep potatoes from sticking to bottom of pot. Simmer until potatoes are tender but not overcooked.
Add corn niblets and cream (optional) and adjust seasoning. Keep warm.
In a large pan bring the remaining poultry stock to a boil and add the turkey strips and green peas. Simmer 3 minutes.
Serve the chowder in large, flared bowls adding some of the turkey and pea mixture to each.
Garnish with your choice of herbs.