Old-Fashioned Shepherd's Pie

Ingredients

• 1 tbsp extra virgin olive oil
• 500 g lean ground lamb
• 1 large onion (finely chopped)
• 3 carrots (finely chopped)
• 3 stalks celery (thinly sliced)
• 2 leeks (thinly sliced)
• 1 tbsp tomato sauce
• 1 tbsp Worcestershire sauce
• 1 1/3 cups reduced-salt beef stock
• 1/2 cup split red lentils
• 3 tbsp parsley (chopped)
• sprigs parsley (to garnish)
• 500 g potatoes (peeled and cut into chunks)
• 500 g parsnips (cut into chunks)
• 1/3 cup low-fat milk
• 2 tbsp reduced-salt margarine
• pepper (to taste)