Tangy Sauerkraut Soup

It seems that every Eastern European country has their own version of sauerkraut soup. Many of them involve pork, which complements sauerkraut beautifully, but I was keen to create a vegan version — partly because I want to tempt everyone to give it a try (I have never met anyone who didn’t like sauerkraut soup once they’ve tasted it), and partly because, given all the other strong flavours here, I don’t think meat is necessary. However, if you are an avid meat-eater, you could add some por