First make the dressing. Whisk together the oil, lemon juice, caster sugar and garlic. Stir in the mint and chilli, season and set aside.
Cook the broad beans in a pan of lightly salted boiling water for 3 – 4 minutes. Drain and refresh under cold running water. Peel off the grey outer skins. Bring another pan of water to the boil, add the peas and return to the boil. Drain and refresh under cold running water. Place the cooked beans and peas in a large bowl. Add the spring onions and rocket leaves, pour in the dressing, season and toss the salad together.
Preheat the grill to high. Place the halloumi on a greased baking sheet and grill for 2 minutes on each side, until golden and bubbling. Divide the salad between 4 plates, and top each plate with 3 slices of halloumi. Grind over some black pepper and serve.