Heat the olive oil in a large saucepan, over medium heat. Sauté the onion and garlic until softened, about 3 minutes. Add the cauliflower, fennel, macadamia nuts and water and bring to a boil. Reduce the heat to low and simmer until the cauliflower is tender, about 20 minutes. In batches, transfer the soup to a food processor or blender and process till creamy. Return the soup to the pan and stir-in thyme. Heat on medium-low until warm about 5 minutes.