Start by melting the butter in your large pot over medium heat. Once melted, add the minced garlic and chopped onion. Cook, stirring occasionally, until the onion is translucent and the garlic is fragrant – about 3 to 5 minutes.
Toss in the diced carrots and celery. Stir for another 2 to 3 minutes to soften the vegetables slightly. Then, add the diced chicken breast. Cook until the chicken pieces are just opaque on the outside, about 5 minutes, stirring frequently to prevent sticking.
Sprinkle in the dried thyme, salt, and pepper. Stir to coat the chicken and veggies with the herbs and seasoning. Pour in the chicken broth, scraping the bottom of the pot with your spoon to lift any browned bits.
Bring the soup to a gentle boil, then reduce the heat to low. Let it simmer uncovered for about 15 minutes to allow the flavors to meld and the chicken to cook through completely. Finally, stir in the cooked rice. Heat everything together for another 5 minutes to warm the rice through.
Taste and adjust the seasoning with more salt and pepper if needed. Ladle the soup into bowls and sprinkle generously with fresh chopped parsley. Serve hot and enjoy the rich, garlicky goodness.
