Toasted Hazelnut Toffee

to make the toffee

1. Put the butter, sugar, water, corn syrup, and salt in a heavy medium sized saucepan over medium to medium high heat.
2. Stir to combine everything and dissolve the sugar as the butter melts. When the mixture begins to boil, stir only occasionally, and let cook until it registers 300F on a candy thermometer or an instant read thermometer. It will start out as a pale liquid but will start to darken and turn golden. You can start checking the temperature when you see the mixture start to darken.
3. When you have reached 300F remove from the heat and quickly stir in the baking soda and toasted nuts. Be careful at this stage, it is hot!
4. Immediately pour the toffee onto your prepared baking sheet and spread out with an offset spatula, if necessary. The toffee will start to set up right away, so act quickly. You can spread it out very thin, or leave it a little thicker, it's up to you.
5. Let the toffee harden on the baking sheet at room temperature. This won't take very long, under an hour for sure.
6. Carefully peel off the foil and use a large knife to break the toffee into pieces. It will likely shatter rather than cut in neat squares, and that's to be expected.
7. Store the toffee at room temperature