Bring the vegetable stock to the boil, finely chop the onion, add and cook for 5 minutes. Dice the Gorgonzola and mix well with the processed cheese in the simmering soup. Simmer for another 5 minutes. Meanwhile, cut the tomato into small pieces and crumble the sheep`s cheese. Add both and simmer again for 5 minutes. Garnish with chopped basil or with whole leaves and serve.