Drain the mackerel and blot dry. Cut into bite sized pieces and place in a bowl. Roughly chop the tomatoes and shallots and add to the capers and broad beans.
Place the rocket in a food processor with the olive oil and lemon and blend until chopped and well combined. Mix through the salad and set aside for approx 40 minutes to allow the flavours to marinate before serving.
Note: Young broad beans should be tender enough to eat with the skins on. If the beans are large, take the extra step of popping the beans from the skin by making a small incision in the skin and pinching the bean out with your thumb and forefinger.
Makes 4 servings