Line an 8x8-inch or 9x9-inch square baking dish with parchment paper or aluminum foil, leaving some overhang for easy removal. Lightly grease with nonstick spray or butter.
In a medium saucepan over low heat, combine the chocolate chips, sweetened condensed milk, and butter. Stir continuously until everything is melted and smooth—this should take about 5–7 minutes.
Remove the saucepan from heat. Stir in vanilla extract, salt, and marshmallow creme. Mix until fully combined and creamy.
Fold in the chopped pecans or walnuts if using. This step gives your fudge that classic Paula Deen texture and a little crunch.
Pour the fudge mixture into the prepared pan. Use a spatula to spread it evenly. Let it cool at room temperature for about 30 minutes, then transfer to the refrigerator and chill for at least 2 hours or until firm.
Once fully chilled and set, lift the fudge out of the pan using the parchment or foil overhang. Cut into 1-inch squares using a sharp knife. Store or serve as desired.