Put all ingredients except butter and vanilla in a pot and bring to a slow boil. Boil on low heat about 25 minutes or until soft ball stage. (You may scrape down what boils up the sides, but refrain from stirring during this time! ) When fudge reaches soft ball (you can form a soft ball when dripped into cool water), remove from heat and stir in butter and vanilla. Pour into small to medium glass dish that's been sprayed with cooking spray (or buttered). Cool and cut into 24 pieces.