Line a 9×13-inch pan with parchment paper or foil, then set it aside.
Add the sugar, butter, and evaporated milk to a large saucepan. Bring the mixture to a boil over medium heat. Continue boiling, constantly stirring, until the mixture registers 234 F on a candy thermometer, about 5 minutes.
Remove the saucepan from heat and add the chocolate chips and marshmallow fluff, mixing until well combined.
Mix in the walnuts, vanilla extract, and almond extract.
Transfer the fudge to the prepared pan and refrigerate for at least 1 hour before cutting into squares and serving.