Instructions:
- Line an 8x8 inch square baking pan thoroughly with parchment paper, ensuring an overhang on two sides for easy removal later. Lightly grease the paper.
- In a heavy-bottomed medium saucepan, combine the butter, maple syrup, and sweetened condensed milk.
- Place the saucepan over medium-low heat. Stir constantly until the butter is fully melted and the mixture is completely smooth. Do not allow it to boil vigorously yet.
- Increase the heat slightly to medium and continue stirring constantly, scraping the bottom frequently. Bring the mixture to a gentle, rolling boil. Cook (stirring constantly) for 8 to 10 minutes, or until the mixture reaches 235°F (113°C) on a candy thermometer (Soft-Ball Stage).
- Immediately remove the pan from the heat source. Add the white chocolate chips, vanilla extract, and salt. Let this mixture stand undisturbed for 5 minutes to allow the residual heat to melt the chocolate.
- Using a heat-safe spatula, stir vigorously but gently until the chocolate is fully melted and the fudge mixture is incredibly smooth, shiny, and begins to visibly thicken slightly.
- Quickly scrape the fudge into the prepared pan. Use an offset spatula to gently smooth the top; avoid tapping or agitating the pan to prevent graininess.
- Allow the fudge to cool at room temperature for about 30 minutes, then transfer the pan to the refrigerator to chill completely for a minimum of 4 hours, or preferably overnight, until firm.
- Once firm, use the parchment overhang to lift the fudge block out of the pan. Peel off the paper and cut into even squares using a large, sharp knife, wiping the knife clean between cuts.