Vanilla-Bean Ice Cream

Combine cream, milk, sugar, and 1/8 teaspoon salt in a heavy saucepan. Scrape seeds from vanilla beans with tip of a knife into cream mixture, then drop in pods. Heat mixture just to a boil. Whisk eggs in a large bowl, then add hot cream mixture in a slow stream, whisking. Pour mixture into saucepan and cook over moderately low heat, stirring constantly, until slightly thickened and an instant-read thermometer registers 170°F (do not let boil). Pour custard through a fine sieve into a clean metal bowl, then cool, stirring occasionally. Chill, covered, until cold, at least 3 hours. Freeze custard in an ice-cream maker. Transfer to an airtight container and put in freezer to harden.