In a large pot, add oil and leeks. Turn heat to medium high, and cook, stirring occasionally, until golden, about 7-8 minutes. Add garlic and cook until fragrant, about 30 seconds more. Step 2 Add potatoes and cauliflower, season with 1tsp. salt, 1/2 tsp thyme, red pepper flakes and a few grinds of pepper. Add broth, bring to a boil, then reduce heat and simmer, covered, until potatoes and cauliflower are tender, about 20 minutes. Step 3 Remove from heat and, stir in parmesans, and using an immersion blender, blend mixture until smooth.Add more chicken broth if needed.