Lentil shepherd's pie

Ingredients

• 2 medium-sized potatoes, suitable for mashing, peeled and cubed
• 2 tablespoons skimmed milk
• 30g reduced-fat mature Cheddar cheese, grated
• Light cooking oil spray
• 1 onion, diced
• 1 clove garlic, finely diced
• 1 stick celery, trimmed and sliced
• 2 carrots, peeled and diced
• ½ small swede, peeled and diced
• 200g chestnut mushrooms, sliced
• 2 x 390g can green lentils, in water
• 1 tablespoon Worcestershire sauce
• ½ teaspoon each of dried oregano, rosemary and thyme
• ½ –1 teaspoon ground cinnamon
• 400ml reduced-salt vegetable stock
• 1 tablespoon tomato purée