Stir together first 6 ingredients in a 3 1/2-quart saucepan over medium-high heat, and cook, stirring constantly, until mixture comes to a boil. Cook, stirring constantly, until a candy thermometer registers 234° (soft-ball stage) or for about 12 minutes.
Remove pan from heat; stir in remaining ingredients until well blended. Pour into a greased aluminum foil-lined 9-inch square pan. Let stand 2 hours or until completely cool; cut fudge into squares.