In a dry, nonstick saucepan, toast the walnuts over medium heat, until golden and fragrant.
Allow walnuts to cool, chop. Set aside.
In a large saucepan, boil maple syrup over medium heat - stirring frequently - for 8 minutes.
Add chopped walnuts, heavy cream, and milk; whisk well to combine.
Bring mixture to a simmer, stir well, and remove from heat. Allow to sit for 1 hour.
Once the hour is up: beat egg yolks and salt together in a large bowl until fluffy.
Add to cooled maple mixture, whisking until smooth and combined – you don't want any unblended chunks of egg mixture.
Cook mixture over medium high; heat just to the boiling point, whisking constantly. As the mixture begins to boil, remove from heat.
Transfer mixture to a heat safe bowl. Allow to cool to room temperature before covering and transferring to the fridge.
Prepare ice cream according to your ice cream maker's instructions - depending on the size of your ice cream maker, you may need to do this in batches.
Transfer ice cream to an appropriate container. Cover and freeze for at least a few hours, to firm up.