In large saucepan on medium heat, sauté leeks and shallot in olive oil for 2 to 3 minutes. Add garlic and sauté for a few minutes more, until mixture is soft. Add miso, mustard, and 1/2 cup stock and stir to combine. Add beans and simmer for 3 minutes, until beans are warmed. Add kale and remaining stock and cook for a further 3 to 5 minutes, until kale is tender. To serve, place toasted sourdough on plates and pile high with bean mixture.