Dissolve the stock in a good 1 l boiling water and keep it hot. Peel onion and dice very finely. Heat the oil in a pot. Sauté onion in it. Add rice and roast for 1-2 minutes while stirring until the rice grains start to "crackle".
Slowly add some hot stock and stir from time to time. As soon as the rice has absorbed the broth, add broth again and again. Stir in laurel. Simmer rice open at low heat for 18-20 minutes.
Keep stirring it so that nothing sticks. Add some stock until the rice is creamy but still al dente at the core.
Grate pecorino. Fold into the finished risotto pecorino, butter and prosecco. Season to taste with salt and pepper. Let it rest for 1 minute and serve hot.