Line a baking sheet with parchment paper.
Melt butter in a heavy saucepan.
Add sugar and salt. Stir constantly.
Cook mixture over medium heat.
Use a candy thermometer to monitor.
Heat until 300°F, or hard crack stage.
Remove from heat and stir in vanilla.
Pour mixture onto the prepared sheet.
Spread evenly with a spatula.
Sprinkle chocolate chips on top.
Let chocolate melt for 2 minutes.
Spread melted chocolate smoothly.
Sprinkle chopped nuts over chocolate.
Cool completely until firm and hard.
Break into small pieces and serve.