Line a rimmed baking sheet with parchment paper or a Silpat liner.
In a microwave-safe mixing bowl combine the sugar, corn syrup, salt and microwave on high for 3-4 minutes.
Stir in peanuts and microwave 3 more minutes.
Mix in butter and vanilla and stir. Microwave for 1-2 minutes longer.
Quickly stir in the baking soda and vanilla and stir until the butter is melted. Don’t stir too long. Pour onto your baking sheet.
To spread the peanut brittle out, tilt the baking sheet. (TIP: heat your cookie sheet so it’s warm when you put the peanut brittle on it, it will help it spread easier.)
Let cool for 15 minutes.
Break into pieces.
Notes
this is for a 700W microwave. If your microwave is a higher wattage, you’ll need to do this on a reduced power