Grease a baking sheet and set aside. In a glass bowl, combine peanuts, sugar, syrup, and salt until well mixed.

Heat in microwave for 6 to 7 minutes on high until mixture is bubbly and peanuts are browned.

Stir in butter and vanilla; cook for 2 to 3 minutes longer. Quickly stir in baking soda, just until mixture is foamy.

Let cool for 15 minutes or until set. Break into pieces and store in an airtight container.