1. Heat 1 teaspoon of oil in a pan over medium heat. Add one-third of the cauliflower and all the finely chopped garlic. Cook, stirring, for 2 to 3 minutes. Add the broth. Bring the mixture to a simmer and cook with the lid on for 15 minutes until the cauliflower is very tender. Remove from heat. Sprinkle the yeast over the mixture. Use an immersion blender to blend the mixture until smooth.
2. Meanwhile, place the remaining cauliflower in a food processor and pulse until it resembles coarse rice. Set aside.
3. Heat 1 teaspoon of oil in a pan and add the chopped onion, thyme leaves, sliced mushrooms, and 2 tablespoons of water. Cook, stirring regularly, for 10 minutes until the vegetables are tender.
4. Add the cauliflower rice and 50 ml of boiling water. Cook, stirring, for 2 minutes to heat everything through. Stir in the cauliflower puree. Add a little water if the risotto is too thick. Season with salt and pepper. Serve garnished with parsley.