Pasta, ham and fava bean salad

Ingredients

• 300 g fusilli
• 2 1/2 cups shelled baby fava beans (fresh or frozen, thawed if necessary)
• 400 g cherry tomatoes (halved)
• 150 g lean cooked ham (diced)
• 1/4 cup fresh chives (snipped)
• 1 tbsp extra virgin olive oil
• 50 g watercress leaves (roughly chopped)
• 50 g watercress leaves
• 1/3 cup walnut pieces
• 1 garlic clove (peeled)
• 1/4 cup extra virgin olive oil
• 1/2 lemon (zest grated and juiced)
• 1/4 cup low-fat plain yogourt