Begin by assembling all the ingredients and preheating the oven to 180 degrees C. You will need a good sized casserole dish and a large pan. Prepare the vegetable stock by filling the kettle and placing a veg stock cube in a jug ready for adding to the pan.
Begin by adding the oil to the pan and turning the heat to a med-high setting. Once it begins to heat, add the onion and celery and stir. Turn down the heat to low and add a lid to the pan. Allow to cook for around 7 minutes until the onion and celery begin to soften.
Now add the chopped carrots, parsnip, and sweet potato chunks. Return the lid and allow to cook for a further 10 minutes on a low heat.
After around 10 minutes, stir in the flour, then the yeast extract, black pepper and the tomato puree. Now add a little of the vegetable stock while stirring constantly. Continue stirring over the heat while slowly adding the rest of the vegetable stock. Add the dried rosemary and then allow the pan to simmer for 5 minutes with the lid firmly on.
Turn off the heat for the pan and stir through the chestnuts. Carefully add the mixture to the casserole dish, cover with foil and place in the oven to cook for 30 minutes or until all the vegetables are tender for eating.
You do not need extra salt with this recipe as the yeast extract is already high in salt.
You can use marmite or vegemite as the yeast extract.
You can prepare this meal up to the point of adding to the oven, in advance if needed then store it in the fridge until ready for cooking. Just increase the oven time as it will take an extra 10 minutes from chilled.