Line an 8” baking pan with foil and spray with cooking spray.
In a large saucepan, combine the maple syrup, both sugars, evaporated milk and salt.
Bring to a boil over medium high heat, stirring constantly.
Once boiling, stop stirring, and cook for 7-8 minutes, until the mixture reaches a temperature of 238 °F on a candy thermometer.
Remove from heat and add in the butter and vanilla extract (be careful, it will bubble when you add them!)
Using a handheld electric mixer, carefully beat the mixture for about 5 minutes, until the mixture has thickened and loses its glossy appearance. Do not overbeat! It will become dry and crumbly if you do.
Pour the mixture into the prepared pan and evenly spread out.
Sprinkle with the chopped walnuts.
Allow to cool for at least 25 minutes.
Remove the fudge from the pan using the foil and cut into 12 squares.
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