In a glass 1.5 qt casserole or mixing bowl, stir the corn syrup and granulated sugar together and microwave for 3.5 minutes. Stir in the peanuts and microwave for 3 more minutes until light brown. Add the butter and vanilla to the mixture and stir until well combined. Microwave for an additional 1.5 minutes.

You will need to work quickly for the next step, so be sure to have your buttered cookie sheet ready to go. Add the baking soda to the mixture and gently stir until light and foamy. Quickly pour the foamy mixture onto the greased cookie sheet.

Do NOT use a spoon to spread the mixture around. Instead, gently rotate the pan to spread the mixture around until it is about 1/2 inch thick. Work quickly, because it will began hardening very fast.

Let the peanut brittle cool for at least 1/2 hour or until it is hard and smooth to the touch. When it is cooled, break the candy into small pieces and store in an air-tight container.