Line the outside of the spring-form pan containing the crumb base with a good wrapping of plastic wrap, so that the whole of the bottom and sides are enveloped in plastic. Do the same with aluminum foil, covering the layer of plastic wrap to make a very watertight casing. (NOTE: If you can find it, the LARGE size aluminum foil and is much more effective at keeping the pan water-tight. I recommend it.)
Beat the cream cheese until smooth and add the sugar. Add the eggs and egg yolks, beating them in one by one until they are incorporated into the cream cheese and sugar. Make sure to scrape the sides and bottom of the bowl once in a while. Pour in the sour cream, vanilla extract and Frangelico, and beat again until smooth and creamy. Finally fold in the ground praline. Place the spring-form pan in a roasting pan and pour in the batter.
Pour water from a recently boiled kettle into the roasting pan to come just over an inch up the side of the pan and place in the oven to cook for an hour.
When the cheesecake is ready it should be just set on top with a hint of wobble underneath; it certainly carries on cooking as it cools. Take the cheesecake out of the roasting pan, take off the foil and plastic wrap and let the cheesecake cool on a rack.
It will need to chill for at least 3 hours, though overnight it best. It can be made 2 days ahead.