2 TBS of olive oil
1 small yellow onion (1/2 cup diced) (I used a large white onion)
2 cups of diced raw sweet potatoes
2 cups of diced raw white potatoes
4 cups of vegetable stock (I used chicken broth)
2 cups of pure water
half of lemon freshly squeezed for juice  

THE SPICES
1 tsp. of sea salt
1 tsp. of black pepper
1 TBS of minced garlic powder
1-2 tsp. of ground ginger
1 tsp. of ground paprika
1 tsp. of dried marjoram or rosemary
1 tsp. of dried basil
1 tsp. of dried oregano
(I added 1 tsp fresh thyme leaves)
2 bay leaves
handful of chopped fresh parsley or chives

Saute the onion in a large pot with the olive oil for a few minutes, then add the broth, bay leaves, water and diced potatoes. Cook for a few more minutes and then add the rest of the ingredients and bring to a boil. Boil on high for 10-15 minutes and then turn down the heat and let cook until the potatoes start to fall apart in the broth. Use the back of a large ladle or spoon to help the potatoes break up and become a part of the broth. The soup will get much thicker if you do this after about 30 minutes or so. Then after the potatoes have broken down enough to your liking, add some fresh chives or parsley for serving a hot bowl of soup.
From http://glutenfreehope.blogspot.com/2011/01/two-potato-soup-vegan.html