Melt the butter in a large Dutch oven over medium heat. Add the onion, carrots, and celery. Cook for 8 to 10 minutes, stirring occasionally, until softened.
Stir in the garlic and cook for 30 seconds until fragrant.
Sprinkle the flour over the vegetables and cook for 1 minute, stirring constantly.
Add the thyme, parsley, rosemary, onion powder, garlic powder, poultry seasoning, celery seed, bay leaf, salt, and pepper. Stir well to combine.
Slowly whisk in the chicken broth until smooth. Stir in the chicken bouillon paste if using.
Add the wild rice and bring the soup to a gentle boil.
Reduce the heat to low, cover, and simmer for 45 to 55 minutes, or until the wild rice is tender and many grains have split open.
Stir in the shredded chicken and cook for 5 minutes.
Stir in the milk, heavy cream, and Worcestershire sauce.
Simmer uncovered for 10 minutes, stirring occasionally, until the soup is creamy and lightly thickened.
Remove the bay leaf and stir in the lemon juice and fresh parsley.
Taste and adjust seasoning if needed before serving.