Heat olive oil in large pot over medium heat.
Add diced onion and cook until softened completely.
Stir in minced garlic and cook for one minute.
Add sliced mushrooms and cook until golden brown.
Season mushrooms with salt and pepper generously.
Add rice to pot and stir for two minutes.
Pour chicken broth slowly into the rice mixture.
Add dried thyme and bring to gentle boil.
Reduce heat to low and cover pot tightly.
Simmer for eighteen minutes without lifting the lid.
Remove from heat and let rest five minutes.
Fluff rice with fork and add butter.
Garnish with fresh parsley before serving immediately.