I realize this is a bit late, but I'm still happy to answer your question.
In order to pan products, you must have some sort of specialized machine for it; the Kitchen Aid attachment is a good beginning option and not overly costly. From there, stand-alone panning machines can range in the $3000 - $6000 USD range, or even above to $16,000 or more. When purchasing equipment, consider how much product you would have to sell in order to pay for that machine. A large reason people do not do the process anymore is because larger companies have made it so incredibly cheap to buy, and a small confectionery shop would have to charge significantly higher prices to make a profit. While many people are happy to pay for a quality product, there are 10 times more who either cannot or will not choose that option.
There is no standard recipe for panning, just as there is no standard recipe for caramel, ganache, etc.; each chocolatier or confectioner employs their own unique process depending on what ingredient they want to coat, what they want to coat it in, how they want to finish their product (some products are given a glazed or shiny appearance, others are given a truffled appearance) and the equipment they have available.
That being said, there is a standard process that most follow in order to get a quality product. In addition, to my knowledge there is not a lot of information or literature available on the panning process, and very few people actually perform it nowadays. It is mostly something reserved for large confectionery companies, i.e. Mars, Nestlé, etc.
Basic Technical Process:
For sake of example, let's use hazelnuts, however you could use most any nut, or even freeze-dried fruits like bananas, raspberries or blueberries.
That is the basic, and by basic I mean fairly complex and intricate, process. It represents only a small portion of what you may do with panning products, and as always with chocolate, your imagination is the only limit.
A basic quantity recipe you may start with could be:
400 g hazelnuts
135 g sugar + 45 g water (to caramelize the nuts)
1000 g crystallized chocolate
100 g cocoa powder
One final note on the panning process: some people prefer to use non-crystallized chocolate (and may advise you to do so), at a temperature of about 40C (104F), however we do not. We have found better results with a crystallized product than not, but you may certainly experiment yourself.
Feel free to ask any other questions; I will be happy to answer as best I can.
A great, informative post. Thank you.