Peel the onion and garlic. Cut both very finely. Peel the carrot and cut it into very fine cubes. Bring the vegetable stock to the boil and keep it hot on a low flame.
Heat the olive oil in another saucepan and sweat the onion, garlic and carrot cubes in it. Then add the unwashed rice, also sweat it. Deglaze with white wine and let it boil down a little. Then pour in hot broth over and over again and continue to simmer while stirring until all of the broth is used up. This takes about twice as long as with normal risotto. Season the risotto with lemon juice and salt and mix in the plucked oregano leaves and the parmesan.