1. Heat the milk in a medium-size saucepan with the sugar and salt.
2. While that’s heating, pour the cream into a metal bowl and set that bowl into a larger bowl with some ice, creating an ice bath. Set a mesh strainer over the top of the empty bowl.
3. Whisk the yolks in a small bowl and gradually pour some of the warm milk mixture over the yolks, whisking constantly. Scrape the warmed yolks back into the saucepan and cook the custard using a heatproof utensil, stirring constantly (scraping the bottom as you stir) until the mixture thickens. If using an instant-read thermometer, it should read 160-170F (71-77C).
4. Pour the custard through the strainer into the heavy cream set over the ice bath, then stir frequently until the mixture is cooled down. Refrigerate at least 8 hours or until thoroughly chilled.
5. Soak the sour cherries in the eau-de-vie, cover, and let them stand overnight, stirring occasionally.
6. Whisk the oil into the ice cream custard then freeze the mixture in your ice cream maker according to the manufacturer’s instructions.
7. Drain any liquid off from the cherries (which is a tasty little reward for your efforts) and when you remove the ice cream from the machine, fold in the cherries.