Step 1Set near the stove a baking sheet lined with parchment paper that's been greased with butter for the finished brittle and a white plate to use in judging the color of the caramel .
Step 2Mix the sugar and salt and spread it in the bottom of a large, stainless steel skillet. Set the pan over medium-high heat without stirring until the sugar begins to melt into a clear syrup around the edges. Turn the heat down to medium and continue melting the sugar without stirring -- shake the pan to redistribute it -- for as long as the syrup remains clear. When the syrup begins to color, stir it with a silicone spatula or wooden spoon, mixing until the sugar is melted and evenly colored. Drop a bead of syrup on the white plate to judge the color accurately: It should be a reddish amber.
Step 3Add the nuts and stir gently to coat with the syrup. Immediately scrape the contents of the pan onto the buttered parchment and spread the mixture out as thinly as you can. (Do not touch the hot caramel!)
Step 4While the brittle is warm, slide the buttered parchment into a sealable plastic bag and seal until needed. After cooling, break or chop the brittle as desired and return the pieces to the sealed bag to prevent the brittle from becoming sticky.