2 cups sugar
1/2 cup milk
Cook over low heat to 240F on candy thermometer (or soft ball stage). Remove from heat and add:
4 tbsp. peanut butter
1 tsp. vanilla
2 tbsp. butter
Beat until thick and spread in buttered 8 X 8 pan.
The candy thermometer is absolutely necessary for me; otherwise, too much guessing.
This was my Mom's recipe; I personally think it's the best PB fudge I have eaten.