Make peanut brittle in the microwave by cooking the peanut and syrup mixture until it turns golden and thick. Stir in the final ingredients and spread the candy on a parchment-lined baking sheet to cool. Microwaving peanut brittle eliminates the constant stirring of the traditional recipe.
Prepare the baking sheet for the peanut brittle before starting to cook the candy. Spray the rimmed sheet with nonstick cooking spray, add a piece of parchment paper and spray it again.
Prepare the syrup mixture by adding a cup of sugar, 1/2 cup of light corn syrup and 3/4 teaspoon of salt into a large microwave-safe bowl and stirring until it is smooth. Microwave this mixture for two to four minutes until it starts to boil. Remove the bowl from the microwave and stir in 2 cups of roasted peanuts. Place the bowl back into the microwave and heat on high for three to five more minutes until the mixture thickens and turns golden.
Remove the mixture from the oven and stir in 1 teaspoon of vanilla extract and 1 teaspoon of baking soda. Use caution, as the baking soda causes the hot syrup to bubble and foam. Immediately pour the hot mix onto the prepared baking sheet and allow it to cool for 20 to 30 minutes.