In a 1 1/2 quart casserole, stir together sugar and syrup. Microwave on high for 4 minutes.
Stir in peanuts. Microwave on high for 3 to 5 minutes until light brown.
Add butter and vanilla and microwave on high for 1 to 2 minutes.
Add baking soda and gently stir until light and fluffy.
Pour onto greased cookie sheet and let cool. Then break into pieces.
Makes about 24 pieces.