1. In a large saucepan over medium heat, cook the sugar with the evaporated milk, stirring constantly with a wooden spoon until it reaches a boil.

2. Turn down heat slightly, but continue to stir for 6 minutes during a gentler boil. If the mixture begins to brown and stick to bottom of saucepan, turn heat down again, but continue to maintain a boil.

3. Turn off the heat after 6 minutes, then quickly add remaining ingredients, beating constantly until the butter and white chocolate are fully melted, and the mixture becomes well blended, thick and smooth.

4. Immediately pour into cake pan, smoothing the mixture to evenly fill the pan. Take caution when touching the pan; it will quickly become hot. Set aside for 2 hours or until pan and contents are comfortable to the touch.

5. Place pan in freezer for 10 minutes to shrink the fudge from sides of pan for easy removal to a cutting board.

6. Carefully cut fudge into squares with a very sharp knife.