Clean and rough chop cauliflower, garlic, and onion.
Saute' onion and garlic in oil.
Add cauliflower and walnuts.
Add 3 qts water.
Simmer until cauliflower is tender enough to split with a fork.
Puree' mixture and return to pan.
Chop leeks and soak in water to clean.
Add leeks (NOT water) to pan.
Season and serve.