Preheat the oven to 200°C/180°C fan/gas mark 6.
Place the sweet potato in a saucepan of water and boil for 10 minutes or until soft.
Drain the excess water and allow to cool.
Add the oil, swede, carrots, butternut squash, leeks and parsnips to a saucepan and cook for 4 minutes or until they are beginning to soften.
Add the tomato puree, Worcester sauce and sage and cook for another 2 minutes.
Stir in the vegetable stock, season to taste and allow to simmer for 20 minutes.
Pour the vegetable mixture into a small casserole dish and top with the sweet potato slices.
Bake in the oven for 30 minutes.
This recipe has been specifically designed for a low protein diet. Refer to labels for allergen and other product information.