I've made this three times from the NY Times recipe, and tried the original at the restaurant once - here are my findings so far:
The recipe: http://www.nytimes.com/2007/05/09/din...
1) The recipe calls for 1 1/2 tsp kosher salt - I cut it down to 1 tsp, and the pudding was still saltier than Mozza's (but good). In Mozza's version, the salt just amplifies the butterscotch, but doesn't have a distinctly salty presence. When I make it with 1 tsp of salt, the salty note is distinct.
2) The hardest thing for me was to figure out when exactly the caramel was ready, because you're starting off with brown sugar, so you can't rely on color change. The good news is, even if you undercook it (the second time I made it, the "caramel" didn't seize at all when I added the cream) it still tastes good. The last time I made it, I realized that when all of the liquid became froth (meaning, the sugar and water mixture had caramelized to the point where it could hold the shape of a bubble), it was a good time to take it off the stove. Mozza seems to let it go longer - their budino was darker than mine (in fact it was flecked with dark spots).
3) I left out the rum - it doesn't seem to make a difference.
4) The first time I made it, I used 2 cups of cream and 2.5 cups of milk, which gave a slightly lighter texture and less greasy mouthfeel that I liked - however, I think with less fat, it curdles more easily, so straining is even more critical.
5) I prefer it without the whipped cream and caramel - somehow, with the toppings, it seems less rich, and it's actually easier to eat a lot more. I topped it with pine nut brittle (with Maldon sea salt, rosemary, and chile) instead.