This buttery rich toffee is perfect to add to your neighbor treats. Or your own...
Grease jelly roll pan with butter, or line with parchment paper.
Melt butter in large heavy-bottomed pot, add sugar, water, and corn syrup. Stir over medium heat frequently until it reaches the hard crack stage, or 285 degrees. Stir the bottom only, not the sides to prevent crystals. Place candy thermometer in candy once mixture begins to darken in color, almost amber in color. To ensure candy is ready, drop a bit into ice-cold water and roll it between your fingers (let it cool for 10 seconds or so). If it easily rolls into a tight ball, it's ready. If it's still loose and stretchy, it needs more time.
Pour candy into sheet pan once it's reached the hard crack stage. Don't scrap the sides. Spread candy out to reach the edges of the pan. After a couple minutes, sprinkle the chocolate over the hot candy. Let it heat up, and after another 2 minutes, spread it gently with a spatula to cover the chocolate. Sprinkle the chopped nuts and kosher salt, let pan cool. After 2 hours (can place in freezer once it reaches room temperature), break into pieces.