Melt the butter in a pan, slightly fry the shallot then add the rice. Add the wine and let it evaporate on a very high heat. Turn the heat down then add the vegetable stock, one ladle at a time.Squeeze the grapefruit, filter it then put it in a pot and boil. When it is reduced to half, add the remaining butter.

In a pan slightly fry the prawns in 2 tbsp of olive oil. Add salt and pepper.

Pour the grapefruit sauce on risotto and stir. Serve risotto on dishes and put the prawns on the top.