Add olive oil to large soup pot and warm over medium heat; add leeks and scallion for about 5 to 10 minutes. Add cauliflower, chicken stock, milk, cumin, tumeric, salt and pepper. Simmer until flavors have combined, 20 to 25 minutes. Use an immersion blender or remove mixture from pot and blend until smooth. Serve warm, topped with cheddar cheese and crisp bacon (optional), add additional salt and pepper to taste