In a 2-quart microwave-safe bowl, stir together sugar and syrup. (If raw peanuts are used, add now.) Cook for 4 minutes. Stir well. Add salted peanuts, if using. Cook 4 minutes for 650-watt microwave or 2 minutes for 700-watt oven. (ours is 800 watt) Add butter and vanilla to syrup, blending well. Cook 2 minutes longer. Add baking soda and gently stir until light and foamy. If the mixture is not the desired color, return to oven for another 20 seconds. Pour mixture onto a buttered cookie sheet and let cool. Break into pieces to serve. Store in airtight container.