In a medium saucepan, mix the granulated sugar, whole milk, and unsalted butter. Stir until well combined over medium heat.

Bring the mixture to a gentle boil, stirring frequently. Continue cooking until it reaches the soft-ball stage, about 234°F on a candy thermometer, approximately 10-12 minutes.

Once the desired temperature is reached, remove the pan from heat and let the mixture cool undisturbed for about 10 minutes.

After cooling, beat the mixture vigorously with a wooden spoon until it becomes thick and loses its shine, about 5-7 minutes.

Quickly pour the thickened fudge into a greased 8x8 inch square pan and use a spatula to spread it evenly.

Allow the fudge to cool completely at room temperature, which will take about 2 hours. Once set, cut it into squares to serve.