Combine sugar, evaporated milk, and oleo in a saucepan.

Bring the mixture to a boil, stirring constantly.

Continue boiling until the mixture reaches 243°F (soft-ball stage). Use a candy thermometer for accurate temperature readings.

Remove the saucepan from the heat.

Add the chocolate chips, marshmallow creme, and vanilla extract.

Stir well until the chocolate chips and marshmallow creme are completely melted and the mixture is smooth.

Incorporate the chopped nuts into the fudge mixture, stirring until evenly distributed.

Prepare a baking pan by lightly buttering it to prevent sticking.

Pour the fudge mixture into the prepared pan, spreading it evenly.

Allow the fudge to cool completely at room temperature. This may take several hours.

Once the fudge is firm, cut it into squares.