Heat the oil in a large frying pan. Add the onions and brown gently over low heat. Add the garlic, chilli and the mushrooms, stir and fry gently until the mushrooms soften and the juices begin to run. Transfer to a large saucepan.
Add the vegetable stock, wine and black pepper. Simmer for 20 minutes. Add the vinegar and correct the seasoning with salt if needed. Cool and refrigerate until ready to serve.
Heat the mushroom stew. Add the tomatoes and sprinkle with finely chopped parsley. Serve with the soft maize meal.
Make the soft maize meal. Bring the water to the boil and add the turmeric and salt. Slowly stir in the maize meal. Cook over low heat for 5 minutes, stirring frequently. Stir in the cream, if using, and then cover the saucepan and set aside for 1 hour to thicken.