In a large pot, over medium-low heat, add butter and saute the onions, garlic, celery, and carrots stirring often, until onions are translucent about 10-12 minutes.
Sprinkle vegetables with flour and cook over medium heat, stirring often, for 1-2 minutes.
Remove pot from heat and slowly whisk in broth until smooth.
Return pot to heat, add chicken broth, Better Than Bouillon, thyme, bay leaf, salt, black pepper bring to a boil, then immediately reduce heat and simmer, uncovered, for 15-20 minutes.
Mix in peas and chicken and simmer until heated through about 7-8 minutes. Remove and discard thyme stems and bay leaf. Whisk in heavy cream and sherry. Adjust seasoning. Ladle into individual bowls. Garnish with oyster crackers, chopped parsley, and chopped thyme. Serve.