Prepare the Pan – Line an 8x8-inch baking dish with parchment paper, leaving extra over the edges for easy removal.
Heat the Sugar Mixture – In a medium saucepan, combine sugar, heavy cream, butter, and salt. Cook over medium heat, stirring constantly until the sugar dissolves and the mixture starts to boil. Let it simmer for 5 minutes, stirring frequently.
Melt the Chocolate – Remove from heat and immediately stir in marshmallow fluff and white chocolate chips until smooth.
Add Flavor and Color – Stir in the mint extract and add green food coloring if desired, mixing until evenly combined.
Fold in Oreos – Gently fold in the chopped Mint Oreos, reserving some for topping.
Set the Fudge – Pour the mixture into the prepared baking dish, spreading it evenly. Press the remaining Oreo pieces on top.
Chill and Slice – Let the fudge cool at room temperature for 2 hours, then refrigerate for at least 4 hours or overnight. Once set, lift it out of the pan and cut into squares.