In a large saucepan, heat the olive oil until shimmering. Add the onion and leek and cook over moderate heat, stirring frequently, until softened but not browned, about 10 minutes. Add the coriander seeds, garlic, bay leaves and horseradish and cook until fragrant, about 2 minutes. Add the chopped tomatoes, chicken stock and sugar, cover and cook over moderate heat until the tomatoes are softened, about 10 minutes. Discard the bay leaves.