Lay out 2 sheets of parchment paper or silicon mats on a heat proof surface. You can use your counter top or a baking sheet. It's a good idea to have a trivet for your pot nearby as well.
Add sugar and water to a medium heavy-bottomed pot. Swirl the pot around so the sugar melts.
Place pot over medium-high heat and bring the sugar to a boil.
Once the sugar is bubbling away add a generous cup of walnuts in and mix with a wooden spoon so the nuts are completely coated. Sprinkle salt on and continue to mix the nuts regularly as the sugar caramelizes.
When the sugar is golden brown remove pot from heat and use forks or tongs to quickly remove the nuts one at a time, or in small groups and place on the prepared parchment or silicone sheets.
Use your forks to separate any nuts that are touching and allow to cool completely.
Notes
Use a Heavy bottomed pot for this. If you use a thin pan the side gets REALLY hot and can burn the sugar.
Leave the walnuts in the pot when they're done and quickly transfer them one by one or in small groups to a sheet of parchment paper. They will cool down much quicker and be harder to separate if you dump them all out at once.
The walnuts are done once they reach a golden brown color. Stir, stir, stir and keep an eye on them as they will burn quickly.
Normally I'm all about toasting nuts BUT they are basically toasting in the HOT sugar so go ahead and just use raw nuts.
You can sprinkle on spices like cinnamon toward the end of cooking in the sugar. Just mix together a bit before separating.
I love a sprinkle of sea salt just after they're spread out on the parchment paper.