Preheat the oven to 350 degrees F. Line a large baking sheet with parchment paper or a silicone baking mat.
In medium mixing bowl, combine powdered sugar, rosemary, cinnamon and salt. Set aside.
Fill medium saucepan halfway with water and bring to a boil.
Add walnuts to boiling water and blanch for three minutes.
Strain blanched walnuts well and add to the sugar mixture. Toss to coat until well-mixed and sugar have dissolved.
Spread walnuts onto a baking sheet and bake for 18-22 minutes, or until walnuts are golden. Stir every few minutes and keep an eye on them to make sure the sugar isn't burning.
Remove from oven and allow to cool. Store in airtight container.
Pay attention: The sugar can very quickly go from perfectly browned to burnt. So no matter which method you use, keep an eye on the caramelized walnuts to avoid having to start over!
Don’t use wax paper: Parchment paper or a Silpat sheet (silicone making mat) are important to avoid the nuts sticking to the pan. However, they will melt the wax on the wax paper and become an even bigger mess – so avoid!
Use a heavy-bottomed pan: When using a stovetop method, use a heavy-based pan; otherwise, the sugar can burn more easily.
Use a nut/seed blend: This method doesn’t just work for delicious, caramelized walnuts. You can also make a nut blend, nut and seed blend, or even omit nuts altogether and just use seeds (reduce the cooking time accordingly).
For extra flavor: As soon as the rosemary spiced nuts come out of the oven, you can season them with some additional chopped rosemary and possibly flaky sea salt (to taste).