1. Spread the nuts on a baking sheet, keeping the almond separate, and toast the nuts in a 350ºF (180ºC) oven, stirring a few times, for 10 to 15 minutes, until the hazelnuts are browned.
2. While they are roasting, warm the whole milk and powdered milk in a small saucepan with the honey and salt just until it starts to boil. Remove from heat.
3. In a clean, dry bowl set over a pan of barely simmering water, or in a microwave oven, melt the chocolates together until smooth.
4. Once the nuts are well-toasted, remove them from oven and use a spatula to place the warm hazelnuts in a clean tea towel, then fold them inside the towel and rub them vigorously to remove any loose skins. They don’t need to be pristine; just try to get as much off as possible.
5. In a food processor, grind the warm hazelnuts and almonds until they’re as fine as possible. You may not be able to get them completely smooth, depending on your food processor. (I have a brand new one and even after five minutes, there were little bits of nuts in mine, which is normal.)
6. Add the melted chocolate and continue to process the mixture, stopping to scrape down the sides of the work bowl, as necessary.
7. Once the mixture is smooth, add the warm milk mixture and process until everything is well-combined.
(The original instructions here said to strain the paste, which I didn’t do because I don’t mind the little bits of toasted nuts, but you can.)
9. Transfer the mixture into two jars and refrigerate until ready to use.