Brian Turner cooks vegetable casserole with leftover potatoes, red peppers and onions for the festive season on Christmas Kitchen with James Martin.

Brain says: “This hearty vegetarian casserole is quick, easy and cheap as chips to make – plus, it’s handy for using up leftovers.”

The ingredients for the casserole are: 4 tbsp rapeseed oil, 2 carrots, chopped, 2 celery stalks, chopped, 500g roasted chicken bones (optional), 1 garlic bulb, crushed slightly with a rolling pin, 100g tomatoes, chopped, 2 sprigs fresh thyme, 2 tbsp chopped parsley stalks, 3 large onions, chopped, 2 tbsp chopped fresh coriander, 3 large red peppers, thinly sliced, 6-8 leftover roast potatoes, thickly sliced, 50g butter, melted, salt and freshly ground black pepper.

For the mushrooms: 1 tbsp oil, 1 garlic clove, sliced, 340g Portobello mushrooms, sliced and 2 tbsp chopped fresh coriander.