Line the baking dish with parchment paper, allowing some overhang on the sides for easy removal later. Set aside.
In a medium saucepan, combine the maple syrup, heavy cream, granulated sugar, and salt. Stir over medium heat until the sugar dissolves.
Attach a candy thermometer to the saucepan and bring the mixture to a boil, stirring frequently. Continue cooking without stirring until the mixture reaches a temperature of 235°F (112°C), known as the soft-ball stage.
Once it reaches the desired temperature, remove the saucepan from the heat. Add in the unsalted butter and allow it to melt without stirring for a couple of minutes.
After the butter has melted, stir in the vanilla extract and toasted pecans.
Using a wooden spoon or spatula, beat the mixture until it thickens and becomes slightly dull in color (about 5-7 minutes).
Pour the fudge mixture into the lined baking dish and spread it evenly. Let it cool at room temperature for at least 2 hours until set.
Once cooled, lift the fudge out using the parchment paper overhang and cut it into 16 equal pieces.