What to do when you really want a recipe and a restaurant won’t hand it over? At Food Network Kitchens, we try and try again until we figure it out. The Cheesecake Factory has had its signature recipes locked up tighter than a CIA brief since founder David Overton opened the original location in Beverly Hills in 1978. We asked — OK, begged — for the pumpkin cheesecake recipe, and when we couldn’t get it, we ordered the real thing online and reverse-engineered this copy. Try it yourself and…