'A candy/deep-fry thermometer; a 9x5" or 8x4" loaf pan'
Preheat oven to 350°F
Toast pecans on a rimmed baking sheet, tossing once, until fragrant and slightly darkened, 10–15 minutes
Let cool, then coarsely chop
Meanwhile, butter loaf pan
Attach candy thermometer to a large heavy-bottomed pot or Dutch oven set over medium heat
Cook maple syrup, cream, and salt, whisking constantly, and bring to a boil
Stop whisking and continue to boil until thermometer registers 238°F, about 40 minutes
Immediately remove from heat and let cool to 130°F, about 40 minutes
Transfer to a stand mixer fitted with the paddle attachment (or use an electric mixer or wooden spoon) and beat on medium speed until fudge is stiff and opaque, about 12 minutes
Fold in pecans
Scrape fudge into prepared pan; smooth surface
Chill until cool and firm, about 2 hours
Fudge can be made 1 week ahead; tightly wrap and chill