Healthy Shepherds Pie

Name: Healthy Shepherd’s Pie
Ingredients: 250g lean lamb mince; 2 onions, peeled and chopped; 3 carrots, peeled and diced; 2 celery sticks, diced; 2 cloves of garlic, crushed; 200ml of lamb or beef stock; 1 tbsp Worcestershire sauce; 1 tsp Vegemite; 1 x 400g tin lentils, drained and rinsed; 1 small sweet potato, peeled and chopped; ½ head of cauliflower, chopped; 2 tbsp sour cream or natural yoghurt; 1 bunch chives, chopped; Salt and pepper, to taste