Heat olive oil (2 tablespoons) in a large Dutch oven over medium heat. Add mushrooms (12 ounces) and cook until they begin to brown, about 8 minutes. Transfer to a medium bowl and set aside. Add butter (2 tablespoons) to the Dutch oven and cook onion (1), garlic (4-6 cloves), carrots (4), and celery (4) until they begin to soften for about 10-12 minutes. Add mushrooms back to the pot. Sprinkle flour (1/4 cup) over veggies and cook for 1 minute, stirring constantly.
Add broth (64 ounces), thyme (1 teaspoon), Better than Bouillon (1 heaping tablespoon), rice (1 1/2 cups), 1 1/2 teaspoons salt, and 1 teaspoon pepper, and bring to a boil. Reduce the heat to medium-low and gently simmer, partially covered, until the rice is just tender for about 25-30 minutes.
Add corn (1 1/2 cups), chicken (4 cups), and heavy cream (1 cup) to the soup and simmer gently to blend flavors, 10-15 minutes. Adjust seasoning and serve. Sprinkle parsley (2 tablespoons).
Notes
Use a Dutch oven. Its thick walls distribute heat evenly and prevent scorching.
Chop veggies evenly. Similar-sized pieces cook at the same rate and make every bite balanced.
Don’t skip browning the mushrooms. It deepens their flavor and improves texture.
Let the soup rest a bit. The texture gets even better after sitting 10–15 minutes.
If reheating leftovers, add a splash of broth. The rice will continue to absorb liquid as it sits.