Mix peanuts, sugar, corn syrup, and salt in a glass mixing bowl. Cook 6 to 7 minutes on high (700W). Mixture should be bubbly and peanuts browned. Quickly stir in butter and vanilla, cook 2 to 3 minutes longer. Add baking soda and stir quickly, just until mixture is foamy.

Pour immediately onto greased baking sheet. Let set 15 minutes or longer. Break into pieces and store in airtight container.