Heat 2 tbsp of olive oil in a large casserole/saucepan and add the diced onion and celery. Cook for 6-8 minutes over a medium heat until turning translucent, stirring now and then. Then add the crushed garlic and cook for another minute.
Add your diced parsnip and all the herbs and spices to the pan, stir everything, then pour in the hot stock. Bring to a simmer, cover with a lid, and cook for 25 minutes.
Remove the bay leaf and blend the soup, either in a standalone blender or with a stick blender. Return to the dish and season. Serve in bowls drizzled with chilli oil to your taste.
Notes
It's great to make your own chilli oil at home, and it's super simple. However, I also like Chiu Chow Chilli Oil by Lee Kum Kee, which you can find in many shops.
Feel free to omit the chilli oil if the soup already has enough heat for your taste.
If you prefer a sweeter hit of chilli, then you can drizzle hot honey on top of the soup instead.