Preheat the oven to 250. Spread the pecan halves on a large baking sheet. Bake them for 15 minutes.

When there are 5 minutes to go, brown your butter. Cook butter in a medium saucepan over medium heat. Once butter is melted it will foam up a bit, then subside. Keep stirring, a few minutes later the butter will be light brown and then will turn into a deeper brown color, you should be smelling the butter at this point. Takes about 2-4 minutes. Remove pan from heat immediately.

Take pecans out of the oven and put into a saucepan, add brown sugar and rosemary, stir. Once incorporated, arrange pecans back onto a baking sheet. Bake for 15 minutes. Take out of the oven and sprinkle with sea salt. Serve warm or store in an airtight container for a future party.