1. Combine butter, sugar, and water in a large saucepan and heat over medium heat, stirring constantly with a heatproof spatula, until butter is melted and mixture begins to boil, about 5 minutes. Reduce heat to medium-low and continue to cook, stirring constantly and scraping bottom of pot, until mixture is light amber in color and registers 310 degrees, 10 to 12 minutes.
2. Working quickly, remove saucepan from heat and stir in nuts. Transfer toffee to a rimmed baking sheet and spread into a thin, even layer about 1/8" thick. Sprinkle chocolate chips evenly over hot toffee and let sit until softened, about 2 minutes. Spread chocolate all over surface of toffee.
3. Sprinkle toffee evenly with coconut and salt (if using) and let sit 10 minutes. Transfer to refrigerator and chill until chocolate is hardened, about 1 hour. Break toffee into roughly 2" pieces, transfer to an airtight container, and refrigerate for up to one month.
Source: Hannaford fresh Magazine, December 2018