In a 2-quart microwave-safe bowl, combine sugar and corn syrup. Heat, uncovered, on high for 3 minutes; stir. Heat 2 1/4 minutes longer.
Stir in peanuts, butter and cinnamon. Microwave, uncovered on high for 20 to 30 seconds or until mixture turns a light amber color (mixture will be very hot).
Quickly stir in baking soda and vanilla until light and foamy. Immediately pour onto a well-greased baking sheet and spread with forks.
Let cool until firm; break into small pieces. Store in an airtight container. Makes 3/4 pounds.
Note: This recipe tested on a 1,100-watt microwave. If your microwave varies significantly from this, you wild need to adjust the cooking times or use the stove top instructions below.
Stove Top Instructions:
Heat and stir sugar, syrup, and 1/2 cup water in a heavy 3-quart saucepan until sugar dissolves. Cook over medium heat to softball stage (234 degrees).
Add peanuts. Cook to hard crack stage (305 degrees), stirring often. Remove from heat.
Stir in butter, cinnamon and vanilla. Quickly stir baking soda. Pour at once onto two well-buttered cookies sheets, spreading with forks until thin. Break up into pieces when cold.
Notes
You may also use Raw Spanish Peanuts. If you do, add 1/4 teaspoon salt along with the peanuts.