Line a baking sheet with parchment paper.
In a heavy-bottomed small saucepan, melt the butter over medium heat.
Add the sugar and salt and whisk until combined. Cook, stirring constantly, until the mixture looks like melted peanut butter and a thermometer reaches 146 - 148 °C, about 10 minutes.
When it reaches the correct temperature, carefully, pour the hot toffee onto the parchment paper.
Let cool and harden for 20 minutes.
Use a rolling pin to crack the toffee into small pieces.
Store in an airtight container.
