Cover the bottom of a 9 by 9 pan or small cookie sheet with aluminum foil that has been sprayed with cooking spray. (To use a cookie sheet double the recipe.)
Combine the butter, sugar, and salt in a heavy saucepan.
Bring to a boil over medium heat…stirring often. Bring it to a gentle boil.
Cook until it darkens in color about 10-20 minutes. (technically that is 285 degrees)
If you drop some of the mixture into ice water, wait a bit for it to cool, and it stays hard when you take it out of the water...it's done.
When the toffee reaches the hard crack stage pour it into the sprayed pan.
Immediately sprinkle the top with the chocolate chips. Leave for a minute to soften and the spread gently.
Sprinkle the nuts on top and gently press in.
Pop into the fridge until set.
How do you know when toffee is done without a thermometer?
Fill a bowl or glass with ice water. Using a clean spoon, take a little bit of the toffee and drop it into the ice water. Leave to cool for a moment then take it back out. If it hardens but is soft and pliable in your hands, it's at the soft ball stage. If it it forms a ball and is harder to shape, it's hard ball stage. If it hardens the minute it hits the water and cracks when you take it out and try to form it...it's hard crack. Most toffee recipes want you to go for the hard crack stage.
How long does homemade toffee last?
Store it in an airtight container (the air will soften it) on the counter or in the fridge for up to 2 weeks. You can freeze it for a month, or so.
How do I save toffee that has separated?
There are two good solution if you find that your butter and sugar has separated. The first is to remove the toffee from the heat and whisk and whisk until it has combined. Then put it back on the heat and continue. The second option is to add a couple of tablespoons of very hot water to the toffee and whisk it until the butter and sugar has combined. Both options should help you salvage your hard work!