Red Lentil Cottage Pie

Name: Red Lentil Cottage Pie
Prep time: 15 min
Cook time: 1 h
Total time: 1 h 15 min
Cuisine: British
Ingredients: 1 tbsp olive oil; 2 onions (,finely diced); 1 celery stalk (,finely diced); 2 carrots (finely chopped) (,finely diced); 2 garlic cloves (minced) (,finely diced); 2 tbsp tomato paste; 185g (1 cup) red split lentils; 400g (14.5 oz) can diced tomatoes; 1 tbsp balsamic vinegar; 1 tbsp Worcestershire sauce (Skip if serving a baby/vegetarian); 625ml (2.5 cups) veg stock (*SEE NOTE 1); 1 bay leaf; 900g Sweet Potato, (, peeled and cut into large chunks, approx. 5cm ); 75g (¾ cup) Cheddar Cheese, grated (*Optional)