Cook the 1 cup wild rice blend according to the directions on the packaging.
While the rice cooks, melt 5 tablespoons salted butter in a large heavy-bottomed pot.
Prep 1 yellow onion, 1 cup carrots, 1 cup celery and add to the pot and cook for 5 minutes until the onions and celery are soft and translucent.
Add 1 tablespooon garlic paste and cook for 1 minute, stirring constantly so it doesn't burn.
Sprinkle ¼ cup all-purpose flour and 1 teaspoon mustard powder over the vegetables and stir to coat.
Add 2 teaspoons Herbes de Provence, 1 bay leaf, 2 teaspoons salt , and ½ teaspoon ground black pepper and cook for two additional minutes, constantly stirring so they don't burn.
Add a little of the 6 cups chicken broth and stir with the vegetables, then add in the rest. Simmer for 20 minutes.
Add in the shredded 1¼ pound chicken breasts, 1 cup heavy cream, and the cooked rice and simmer for an additional 10 minutes.
Discard bay leaf before serving. Add more cream, salt, and pepper to taste. Increase chicken broth for a thinner soup.