Prepare Your Equipment: Grease an 8×8-inch baking dish with butter or line it with parchment paper. Set aside.

Mix The Base Ingredients: In a heavy saucepan, combine butter, sugar, milk, chocolate, salt, and corn syrup. Continue to stir the mixture over medium heat until it begins to boil.

Boil To Perfection: Once boiling, reduce the heat to low and attach a candy thermometer. Continue cooking without stirring until the thermometer reads 234°F (soft-ball stage).

Cool The Mixture: Remove the saucepan from the heat. Let the mixture cool to 110°F without stirring—this step is crucial for achieving the perfect fudge texture.

Add Vanilla And Beat: Mix the vanilla extract into the mixture. Whip the mixture vigorously with a wooden spoon at the point it thickens and loses its glossy appearance. This may take about 5-10 minutes.

Add Nuts And Pour: If you have chosen to use walnuts, be sure to fold them in. Pour the fudge into the prepared baking dish quickly and spread it evenly.

Cool And Cut: Before slicing the fudge into squares, let it cool fully at room temperature.