Grilled Ox Liver with Creamed Mustard Onions

Being a chef, I’ve always been obsessed with cooking expensive calf’s liver from Holland. I then discovered that ordinary beef liver has similar eating qualities - it doesn’t need to be stewed for hours, as our parents and grandparents used to. In fact most offal can cope with brief flash-frying or grilling. You will pay next to nothing for ox liver, as butchers tend to think it has little value.