How to Make It
In a bowl, combine the olive oil, vinegar, basil, garlic, crushed red pepper and minced rosemary. Season the dressing with salt and pepper.
In a large bowl, combine the beans with the mackerel and onion and toss gently. Add the dressing and toss again.
Mound 1/4 cup of salad on each toast, garnish with rosemary sprigs and serve.