In a medium saucepan, saute red onion over medium heat in the olive oil until soft and translucent.

Add diced chorizo and cook until cooked through.

Add sugar, beans and flour and stir thoroughly. Then add tomatoes, soy sauce, seeded mustard and Worcestershire sauce. Mix thoroughly then add water and bring to a steady simmer and cook approximately 15 mins until beans are soft and the mixture has thickened. Season with salt and pepper to taste.

Serve hot, scattered with fresh basil leaves and toasted croutons.