Heat a soup pot / utensil and add 1 tablespoon olive oil. Add chopped onion and garlic and mix well until the onion appears pinkish.
Add cornflour and mix well. The onion should be coated with cornflour.
Add ½ cup water and ½ cup milk and mix well.
Add roasted cauliflower and let it simmer for 5 minutes.
Switch off the gas. Using a hand blender, blend the roasted cauliflower and onion mixture in the kadai. Ensure that there are small pieces of cauliflower in the soup.
Again place the soup pot on the gas.
Add remaining ½ cup water and ½ cup milk and stir well. If needed add more water to get the thickness that you desire.
Add pepper powder and salt to taste.