Meanwhile, heat 2 tablespoons olive oil in a large pot over medium-heat. Add the leeks and sauté until tender, about 10 minutes (do not brown). Stir in the potatoes, salt, pepper, thyme, and bay leaf. Add the vegetable broth and bring to a boil. Reduce the heat, cover, and simmer until the potatoes are completely tender, 25 to 20 minutes.