Melt 1 tablespoon of the butter in a 2 quart saucepan over medium heat. Add the onion, and cook, stirring occasionally, until tender but not browned, about 8 minutes. Add the rice and cook, stirring, for about 1 minute to slightly toast the grains. Add the wine, increase the heat to medium high, and cook until almost all of the wine has been absorbed and evaporated. Add about 1 cup of the broth, and cook, stirring every minute or two, until almost all of the broth has been absorbed. Continue cooking, adding more broth, and stirring in this manner until the risotto is creamy and al dente, 20 to 25 minutes. Add the remaining 1 tablespoon of the butter and the cheese. Stir briskly to incorporate and melt the cheese. Stir in the whipped cream, taste, and season with salt and a few good grinds of the pepper. Spoon the risotto into six warm bowls or onto rimmed plates. Garnish each with as much shaved fresh truffle as you can afford, a few drops of truffle oil, and some fleur de sel.