Place the sugar in a heavy-bottomed saucepan over medium-high heat. Add just enough water to give the sugar a wet sand consistency. Cook until caramelized. Add the hazelnuts and the almonds and mix with a wooden spoon until coated. Cook until everything is nicely coated and caramelized (dark in color). Remove from the heat and pour onto a sheet of parchment paper. Allow the mixture to cool for a few hours. When cooled, use a food processor to break up the caramelized nuts. Add the peanuts to the food processor and grind until the nuts release their oils and form a paste with the consistency of smooth, old-fashioned peanut butter. Using a double boiler, melt the cocoa butter until completely smooth. Combine the cocoa butter with the chopped bittersweet chocolate until tempered. Mix the chocolate cocoa butter into the nut paste. Add the salt and mix until combined. Pour the mixture onto a plastic wrap-lined sheet pan. Allow to set for a few hours or overnight.
When cooled, use an offset spatula to coat the top of the mixture with the milk chocolate. This will be the top of the finished candy so make this layer of milk chocolate a little thicker than you will on the bottom layer. When the chocolate has set, cover with parchment paper and flip over to expose the uncoated side. Using an offset spatula, coat this side of the mixture with milk chocolate. When the chocolate has set, use a sharp chef's knife or a rolling cutter to cut into the desired sized pieces.
How to Temper Chocolate:
Chocolate is tempered so that after it has been melted, it retains its gloss and hardens again without becoming chalky and white (that happens when the molecules of fat separate and form on top of the chocolate). There are a variety of ways to temper.
One of the easiest ways to temper chocolate is to chop it into small pieces and then place it in the microwave for 30 seconds at a time on high power until most of the chocolate is melted. Be very careful not to overheat it. (The temperature of dark chocolate should be between 88 and 90 degrees F, slightly warmer than your bottom lip. It will retain its shape even when mostly melted. White and milk chocolates melt at a temperature approximately 2 degrees F less because of the amount of lactose they contain.) Any remaining lumps will melt in the chocolate's residual heat. Use an immersion blender or whisk to break up the lumps. Usually, chocolate begins to set, or crystallize, along the side of the bowl. As it sets, mix those crystals into the melted chocolate to temper it. A glass bowl retains heat well and keeps the chocolate tempered longer.
Another way to temper chocolate is called seeding. In this method, add small pieces of unmelted chocolate to melted chocolate. The amount of unmelted chocolate to be added depends on the temperature of the melted chocolate, but is usually 1/4 of the total amount. It is easiest to use an immersion blender for this, or a whisk.
The classic way to temper chocolate is called tabliering. Two thirds of the melted chocolate is poured onto a marble or another cold work surface. The chocolate is spread out and worked with a spatula until its temperature is approximately 81 degrees F. At this stage, it is thick and begins to set. This tempered chocolate is then added to the remaining non-tempered chocolate and mixed thoroughly until the mass has a completely uniform temperature. If the temperature is still too high, part of the chocolate is worked further on the cold surface until the correct temperature is reached. This is a lot of work, requires a lot of room, and makes a big mess.
A simple method of checking tempering, is to apply a small quantity of chocolate to a piece of paper or to the point of a knife. If the chocolate has been correctly tempered, it will harden evenly and show a good gloss within a few minutes.
From Dessert Circus, Extraordinary Desserts You Can Make at Home, .