Place a pot on the stove over medium heat.
Pour in the sugar and let it melt or caramelize. This can take anywhere from a few minutes to 15-20 minutes. Keep a close eye on it, be patient and don't stir!
When the sugar is totally dissolved, dark in color, and begins to lightly bubble evenly, pour in the nuts.
Immediately transfer to a parchment lined baking sheet. Careful! It's super hot. Quickly spread it out into an even layer. Top with coarse salt if desired and let the brittle cool for at least 2 hours.
Break or cut into pieces.