2-3 large leeks chopped
2-3 potatoes (Yukon Gold are best)
water (Vegetable broth better if have it.)
little sea salt
little olive oil
Heat oil in large pot. Saute onions and chopped leeks. Add potatoes, then water or veb. broth - just enough to cover the vegetables. Add little salt and herbs if like. Boil, let simmer. Either mash into chunky soup or blend smooth.
You could garlic etc, but i find the leeks add an incredible tasty flavour on their own.
Some people don't like to combine vegetables and potatoes, but i find it to be fine...