Preheat oven to 180C. Use a rolling pin to roll bread slices to flatten bread. Combine butter and garlic in a small bowl. Use a 7.5cm round pastry cutter to cut discs from the bread. Lightly brush with butter and press into twenty-four holes of a 30ml (11/2 tablespoons capacity) round based patty pans. Bake for 20 minutes or until golden brown and crisp.

Meanwhile, combine wine, 1 cup (250ml) water, bay leaf and peppercorns in a large saucepan. Place over high heat and bring to the boil. Add chicken breasts. Reduce heat to low and cook for 12 minutes or until cooked through. Transfer to a bowl and set aside to cool. Finely shred chicken.

Combine mayonnaise, mustard and tarragon in a bowl. Add chicken, walnuts, celery and apple and gently toss to combine. Divide chicken mixture among tartlet cases and top with watercress sprigs to serve.