Bring the maple syrup to a boil over medium heat; reduce the heat to low and simmer for about 2 minutes. Add the evaporated milk and bring to a simmer.

In a small bowl, whisk the egg yolks with the salt. Whisking constantly, add about 1 cup of the hot mixture to the egg yolk mixture. Return the egg yolk mixture to the saucepan and continue cooking until the mixture coats the back of a spoon, or to about 170 F. Do not boil.

Remove the custard mixture from the heat and add the heavy cream and vanilla extract; stir to blend. Place a sheet of plastic wrap over the custard mixture and refrigerate until it is thoroughly chilled, about 2 to 3 hours or overnight.

Pour the chilled custard into the ice cream maker and churn following the manufacturer's directions.

Add the chopped walnuts just before the ice cream is ready. Transfer the ice cream to a freezer container and freeze for about 2 hours, or until hardened.

Enjoy!