Heat olive oil on the pan. Chop onion and garlic and mushrooms if using them.
Fry the onion and after about 4-5min add the garlic. For for another 1 min on medium heat. Meanwhile fry the shrimps for 5 min on another pan. Set aside.
Prepare mushroom or normal stock, boil 500ml of hot water and add the stock content. Mix it to combine. If you are using mushrooms fry them with onion and garlic for another 5min on medium heat.
Add rissoto rice to the pan and fry for 2-3 min. Then add half of the stock. Let the water cook out and add another half if necessary. Cook until the rice is done.
Stir in the grated parmesan, add the prawns and serve immediately.