Add the olive oil and butter to a large pot and saute the onion and garlic over medium heat on the stove-top. Continue stirring until the onion has softened and is translucent (approximately 3 minutes).
Add the carrot and celery and cook for a further 3 minutes.
Add the parsley, thyme, bay leaf, chicken stock liquid and water, and stir.
Add the whole chicken breasts and stir, then cover with a lid and allow to cook, just simmering, for 30 minutes (stirring occasionally).
Add the rice, stir and cover again. Cook for a further 15 minutes.
Remove the chicken breasts from the soup and place onto a plate. Using two forks, shred the chicken into pieces. Return the shredded chicken meat to the soup to reheat through.
Discard the bay leaf. Season with salt and pepper and serve.
Notes
RECIPE NOTES AND TIPS
Using dried herbs as a substitute - Dried herbs are much stronger than fresh herbs, so the general rule of thumb is to use ⅓ of the fresh amount.
Using leftover cooked chicken - you can substitute the chicken breasts for leftover cooked chicken or rotisserie chicken. Simply shred the cooked chicken and add at the same time as the rice.
Making homemade croutons: Croutons are crunchy cubes of toasted bread that add crunch and extra flavour to soups. To make your own, cut day-old, slightly stale bread into small cubes. Toss with olive oil and seasonings of your choice - eg paprika, mixed herbs, garlic powder - and bake in a single layer at 180 degrees Celsius until golden brown. This will probably take between 15-20 minutes, and I recommend turning them over halfway through the cooking time.
Freezing leftovers - you'll notice that the liquid will begin to disappear as the soup cools (thanks to the rice soaking up the liquid). I recommend using a slotted spoon to remove the chicken, rice and vegetables and freezing in an airtight container and then freezing the chicken stock liquid in another. When you're ready to use the frozen leftovers, defrost the chicken, rice and vegetables and then add the stock liquid. You may find you need to add a little extra water at this stage.