Add butter to a heavy bottom pot and heat on medium heat.
When butter is halfway melted add in brown sugar and salt and let it melt together and come up to a simmer.
Add in your candy thermometer.
Line a baking sheet with parchment paper while butter and sugar are melting together.
Stirring almost constantly, bring mixture up to 310℉ and immediately pour onto parchment lined baking sheet.
Smooth out the mixture evenly with the back of a spatula.
Let sit uncovered in a cool dry place for at least 20 minutes.
Crack the hardened toffee with a spoon into pieces and blend into a powder. Store in a clean, dry container. Add 1 T to espresso for latte.
