1. Mix the sugar and corn syrup well in at least an 8-cup microwaveable dish (It's easier if you have something with a handle on it).
2. Microwave on high for 3-1/2 minutes, stirring after the first two minutes.
3. Add peanuts to sugar and syrup mixture and microwave on high for 4 minutes, stirring at two minute intervals.
4. Add vanilla and butter, stir, and return to microwave for 1 minute on high.
5. Remove from microwave and stir in baking soda (it will bubble up here, hence the 8 cup container!!).
6. QUICKLY pour onto lightly greased cookie sheet and cool in fridge for 15 minutes.
7. Break apart and store in airtight container.