Butter a cookie sheet. combine sugar and corn syrup in a 2 quart glass bowl and microwave on high for 4 minutes. Stir in peanuts and microwave on high for 3 1/2 minutes more, then stir in butter and vanilla and microwave for 1 1/2 minutes.

Stir in baking soda until light and foamy. Pour onto cookie sheet and spread then. Cool completely and break into pieces and serve.