Spray a wooden spoon (or other heat-proof stirring implement) with non-stick cooking spray. Lightly grease a 10" x 15" or larger baking sheet, or line it with parchment., Mix together the sugar and corn syrup in a large microwave-safe bowl and stir until well combined; the mixture will be stiff and hard to stir. Be sure to use a large enough bowl; the sugar/corn syrup should fill it no more than 1/4 to 1/3 full., Microwave the sugar mixture uncovered on high power for 5 minutes; it will bubble vigorously., Add the peanuts and butter, and stir well to combine. Speed is key! The cooler the mixture becomes the harder it will be to stir., Replace the bowl in the microwave and cook on high for 2 to 4 minutes, until the mixture turns a nice medium-brown caramel color. Start watching carefully around the 2-minute mark, and remove when the caramel color is achieved., Add the baking soda and vanilla. The mixture will bubble furiously upon the addition of these ingredients — this is what gives the candy its hallmark airy texture. (This is also why you need to use a large bowl.) Stir quickly to combine. The finished mixture will look creamy and caramelized., Working quickly, pour the mixture onto your prepared baking sheet and spread it as evenly as possible. If you end up with an uneven spread, don't worry — the candy should still set up nicely, even in the thicker areas., Once the brittle has set and cooled (30 to 60 minutes), break it into pieces.