In a medium pot, heat up the oil on medium heat.
Chop the leeks into small chunks and add it to the pot. Saute for about five minutes, stirring frequently.
Add the white wine and saute for a couple of minutes.
Add the potatoes and vegetable stock. The stock should be enough to just cover the potatoes. Add a little more if needed. Add bay leaf, chopped sage leaves, salt and fresh cracked black pepper and stir well.
Cover but leave a crack for the steam to escape. Cook until the potatoes are done on medium to medium low heat.
Once the potatoes are done, use an immersion blender to puree about half of the potatoes. (I like soup to be a little chunky but if you don't, feel free to puree all of the soup. You can also transfer the potato leek soup into a standing blender to puree.)
Add the heavy cream and finely chopped green onions. Cook for another two-three minutes and serve.