One-Pot Chicken Casserole with Creamy Sherry Sauce

Ingredients

• 2 tbsp olive oil
• 8 skinless boneless chicken thighs, about 1¼ lb total weight
• ½ lb button mushrooms
• 6 oz baby leeks
• 4 small turnips, peeled and quartered
• 1 lb pre-washed small new potatoes
• 2⅓ cups chicken stock, made with a stock cube
• 4 tbsp medium or sweet sherry
• 7 oz green beans
• 1 tbsp cornstarch
• 1 cup plain low-fat yogurt
• grated zest of 1 lemon