Mascarpone is an Italian triple-cream cheese — a dense, glossy, ivory spread made by gently curdling cream with a touch of acid and draining off the whey. Lush and spoonable, faintly sweet and lactic with almost no tang, it is the soft, fatty heart of tiramisu and is folded into risotto, pasta sauces, frostings and desserts wherever a cook wants pure, melting richness.