Line an 8x8x2-inch baking pan with foil, extending the foil over the edges of the pan. Butter the foil; set pan aside.

Butter the sides of a 2-quart heavy saucepan. In saucepan combine sugar, evaporated milk, and butter. Cook and stir over medium-high heat until mixture boils (about 10 minutes). Reduce heat to medium; continue cooking, stirring constantly, for 6 minutes.

Remove saucepan from heat. Add marshmallows, chocolate pieces, walnuts, and vanilla; stir until marshmallows and chocolate melt and mixture is combined. Beat by hand for 1 minute.

Spread fudge evenly in the prepared pan. Score into squares while warm. Cover and chill for 2 to 3 hours or until firm. When fudge is firm, use foil to lift it out of pan. Cut fudge into squares. Store tightly covered in the refrigerator for up to 1 month. Makes about 2 pounds (64 pieces).

Prepare as above, except substitute 1/2 cup peanut butter for the butter and, if desired, peanuts for the walnuts. Nutrition Facts per piece: 58 cal., 3 g total fat (1 g sat. fat), 1 mg chol., 14 mg sodium, 9 g carbo., 0 g fiber, 1 g pro. Daily Values: 0% vit. A, 0% vit. C, 1% calcium, 1% iron Exchanges: 1/2 Other Carbo., 1/2 Fat

In a 2-1/2-quart microwave-safe bowl microwave butter, uncovered, on 100 percent power (high) for 45 to 60 seconds (for 1,000- to 1,300-watt ovens) or 60 to 75 seconds (for 600- to 800-watt ovens) or until melted. Stir in the sugar and evaporated milk. Microwave, uncovered, on high for 7 minutes (for 1,000- to 1,300-watt ovens) or 10 minutes (for 600- to 800-watt ovens), stirring every 3 minutes. Carefully remove bowl from microwave oven. Add marshmallows, chocolate pieces, nuts, and vanilla, stirring until marshmallows and chocolate are melted and mixture is combined. Beat by hand for 1 minute. Pour into prepared pan; continue as above.