Sweet & Salty California Pistachio Brittle

1. Prepare a baking sheet by lining it with parchment paper or a silicone mat. Spray it with non-stick spray or brush it with oil or butter. Set it aside.
2. In a medium saucepan, combine the sugar, corn syrup, and water. Stir them together over medium heat. Put a candy thermometer into the saucepan. Continue stirring and bring the mixture to a boil. Cook it until it reaches 290°F (140°C).
3. Add pistachios, butter, and salt to the pan. Stir everything together. At first, the mixture might become stiff, but it will loosen up again. Keep cooking until the caramel turns a pale amber brown (about 300°F/150°C) and the nuts have a toasty smell.
4. Remove the pan from heat and quickly stir in the baking soda (it will bubble up a bit).
5. Immediately pour the brittle onto the prepared baking sheet. Use an offset spatula or a heatproof rubber spatula greased with a little cooking spray or butter to spread it out as thinly as possible.
6. Sprinkle the Chile-flecked flaky sea salt to your liking on top of the caramel. Let it cool completely.
7. Once cool, break the brittle into pieces. Store the pieces in an airtight container at room temperature.