Slice the white bulb of fennel, discarding the green parts. Break up the cauliflower into florets, add the fennel and cauliflower to a baking tray and drizzle over a generous amount of olive oil and a sprinkle of sea salt.
Bake in the oven for 20-25 minutes until soft and golden, make sure to keep an eye out and not let the cauliflower burn at all.
Heat a large pot over medium heat, add a dash of olive oil. Slice the leeks into rounds and add to the pot. Sauté for 5 minutes until soft. Add in the roasted cauliflower and fennel, nutritional yeast, oregano, stock and soy milk.
Stir to combine, then using an immersion blender, blend until smooth. Alternatively you can skip this step and add all the ingredients into a blender and blend until smooth and then transfer to the pot to warm up.