Peel the celery root. You may need a knife to remove tough outer layers. Scrub it from any excess dirt and debris, and slice the celery root into 1/2 inch cubes. Set aside.

Heat a large pot over medium heat. Add 1 Tablespoon of olive oil to the pot, and once hot add the cubed celery root and onion. Allow the vegetables to cook until soft, stirring occasionally, for about 8 minutes. Make a well at the bottom of the pot. Add the remaining Tablespoon of olive oil and garlic. Cook for another minute, stirring regularly. Season with a pinch of both salt and pepper.

Add the vegetable broth to the pot and bring the mixture to a boil. Turn the heat down to low, cover the pot and simmer gently for 20-25 minutes, until the celery root is soft. Check on the pot occasionally to make sure the heat is not too high or too low.

Turn the heat off and remove the cover. Use an immersion blender or vegetable masher to blend the celery root until smooth. Season with salt and pepper to taste.