The rice is first cooked briefly in a soffritto of onion and butter or olive oil to coat each grain in a film of fat, this is called "tostatura"; white or red wine is added and has to be absorbed by the grains. When it has evaporated, the heat is raised to medium high and very hot stock is gradually added in small amounts while stirring gently, almost constantly: stirring loosens the starch molecules from the outside of the rice grains into the surrounding liquid, creating a smooth creamy-textured liquid. At that point it is taken off the heat for the "mantecatura" when diced cold butter and finely grated Parmigiano-Reggiano cheese are vigorously stirred in to make the texture as creamy and smooth as possible. It may be removed from the heat a few minutes earlier, and left to cook with its residual heat. Seafood risotti generally do not include cheese.