Preheat the oven to 200°C/400°F/Gas mark 6. Mix the dry polenta grains with the garlic and parsley. Into a saucepan, pour the polenta mix into the required amount of boiling water as stated on the cooking packet. Cook polenta until a smooth consistency is achieved. Then pour into a baking tray. Set aside to cool.
In a frying pan, heat the oil and fry the leeks and mushrooms until tender.
Top the polenta with the fried vegetables and add the feta and tomatoes. Bake in the oven for 20mins until the polenta has risen and the cheese has started to melt. Serve immediately.
Notes
For extra flavour, use stock to cook the polenta in instead of water.