Prepare a baking half-sheet pan by lining with a silicone baking mat, or parchment paper or lightly grease with butter.
Combine granulated sugar, water, butter and corn syrup in a heavy-bottomed sauce pan.
Begin heating over medium-high heat stirring occasionally until the mixture begins to boil. Stop stirring once it begins boiling.
Wipe the inside of the pan with a clean brush dipped in cold water to remove any sugar crystals.
Continue to cook until the caramel reaches 300℉. This will take 8 - 12 minutes.
Remove from heat, add the baking soda and stir briefly. Use caution as the caramel may sputter.
Add the shelled pistachios and stir quickly to ensure all nuts are coated with the caramel.
Working quickly, pour the mixture onto the prepared pan. Smooth the mixture with a spatula.
Cool the pistachio brittle completely (about 40 minutes) and break pieces.
Enjoy!
Notes
Please use caution as the caramel is quite hot and may cause severe burns (this is not a good recipe to make with children).
Work quickly once the caramel reaches 300℉. Remove from heat immediately so caramel does not keep cooking, carefully stir in the baking soda (it may sputter when added), stir in the pistachios and spread to desired thickness on prepared pan.
If sugar crystals begin to form on the side of the pan, wipe the inside of the pan with a clean brush dipped in cold water to remove any sugar crystals