In a large sauce pan over medium heat, sauté the leek and garlic in the olive oil until soft.

Add in the chopped bell pepper, carrot, and celery and season everything with salt, pepper and dried thyme. Sauté the vegetables until softened, about 7 minutes.

Add in the chopped cauliflower and vegetable broth and bring everything to a boil.

Once boiling, reduce everything to a simmer and allow the cauliflower to cook for about 10 minutes or until fork tender.

If you have an immersion blender, add the tahini to the pot and puree until smooth and creamy. If using a regular blender, carefully transfer everything in the pot to the blender, add in the tahini and blend until smooth.

Return the blended soup to the pot and taste, adding more seasonings if needed.

Serve warm