First, hack up the white bit of 2-3 leeks and one large potato. It's also fine to use the green part of the leek, but it will result in a slightly darker colour. Sautee them with a bit of olive oil until the potatoes are tender. You don't want them to begin to brown since that will result in a darker soup.
Then, add to a blander jar: a couple hand-fulls (about a cup of leaves) of watercress, the cooked leek and potato and a hand-full of macadamia nuts. I just used regular roasted macadamias.
Blend on medium speed and add water until the mixture is thin enough to puree. Next, ultra puree the mixture! It needs to be completely smooth (I used a Vitamix, for the perfect consistency). When it's very smooth, taste and season it with salt, and if you like, a little squeeze of lemon.
Garnish with a few watercress leaves and a drizzle of macadamia nut oil.