Using a sharp knife, score the duck flesh in a criss-cross pattern on both sides. Put the duck breasts in a a bowl with 1 tablespoon of the olive oil, two-thirds of the garlic, the lemon juice, rosemary and half the thyme sprigs. Leave to marinate while you prepare the rest of the ingredients.
Toast the buckwheat kernels in a heavy-based frying pan over medium heat, stirring and tossing, for 4-5 minutes, until they are darker in colour. Remove from the heat.
Bring the stock to a boil in a saucepan, then stir in the buckwheat. Return to a boil, then reduce the heat, cover and cook over low heat for 10-15 minutes, until the stock has been absorbed and the buckwheat is tender. Remove form the heat and set aside, covered.
Heat a chargrill pan for 10 minutes. Meanwhile, blanch the beans in a saucepan of boiling water for 1-2 minutes. Drain and refresh under cold running water. Cut in half and add to a large salad bowl with the salad leaves, basil, onion and olives, and toss to mix.
Place the duck in the chargrill pan. Cook for 3 minutes, then turn and cook for a further 3 minutes (the meat will be rare, so cook longer if you prefer it well done). Transfer to a board. Place the zucchini, spring onions and tomatoes in the pan and cook for 1-2 minutes, until lightly charred.
Whisk the remaining olive oil and garlic with the vinegar and the leaves from the remaining thyme sprigs in a bowl, then drizzle over the salad. Spoon on the buckwheat, and arrange the hot zucchini, spring onions and tomatoes on top. Season with freshly ground black pepper. Slice the duck and serve on top of the salad.
The duck and vegetables could also be cooked on the barbecue.
Per serving: 572 calories, 36 g protein, 22 g fat (4 g saturated fat), 56 g carbohydrate (10 g sugars), 7 g fibre, 663 mg sodium