1

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

2

Butter the sides of a 2-quart heavy saucepan. In saucepan, combine sugar, evaporated milk, and peanut 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.

3

Remove saucepan from heat. Add marshmallows, chocolate, peanuts (if using) and vanilla; stir until marshmallows and chocolate have melted and mixture is evenly combined. Beat by hand for 1 minute.

4

Spread fudge evenly in prepared pan. Score into squares while still warm. Cover and chill for 2 to 3 hours until firm. When fudge is firm, use foil to lift it out of the pan. Peel off foil and cut fudge into squares. Store tightly in covered container in the refrigerator for up to one month.