Chicken Supreme in an Apple and Leek Sauce

Ingredients

• 1 tbsp butter
• 2 tbsp canola oil
• 4 5oz skinned boneless chicken breasts
• 2/3 cup chicken stock
• 1/4 tsp salt
• 1/4 tsp pepper
• 1 onion (chopped)
• 2 apples (peeled and cut in quarters)
• 2 leeks (sliced in rings or thin slices )
• 1/4 tsp ground nutmeg
• 1 cup plain yogurt