Place a deep pot on the hob with a bit of olive oil and switch it on medium high heat.
Roughly chop your onion and sauté.
Get rid of the knobs of the celeriac root and roughly chop, quarter the fennel and add them both in the pot.
Follow with the chicken broth, bring to the boil and lower to a simmer for approximately 30 minutes or until your vegetables are soft.
Use a handheld blender to mash until smooth and creamy.
For the parsley oil, mince the garlic clove and the parsley leaves and oil in a blender and you are ready to serve.
If you don’t have parsley at hand worry not, you can garnish with the fennel leaves.