• Line an 8x8 or 9x9 pan with foil, letting the edges extend over the sides. Butter the foil and set aside.

For the chocolate fudge:

• In a medium saucepan, melt the sugar, butter and milk, stirring constantly. After the mixture begins to boil rapidly, cook for 4 minutes without stirring, or until a candy thermometer reads 234°F.
• Remove from heat and stir in chocolate, marshmallow fluff and vanilla, beating vigorously until combined.
• Pour into prepared pan, spreading into an even layer. Set aside and allow to cool at room temperature.

For the peanut butter fudge:

• In a medium saucepan, melt the sugar, butter and milk, stirring constantly. After the mixture begins to boil rapidly, cook for 4 minutes without stirring, or until a candy thermometer reads 234°F.
• Remove from heat and stir in peanut butter, marshmallow fluff and vanilla, beating vigorously until combined.
• Pour over chocolate layer, spreading into an even layer. Set aside and allow to cool at room temperature. Cut into small squares and serve.