Yield: makes 1 quart
Active time: 45 minutes
Total time: 45 minutes, plus an overnight chill
Special equipment: ice cream maker
Note:"Vietnamese coffee" in the U.S. often contains ground chicory, but this recipe calls Vietnamese-produced coffee, such as Trung Nguyen, a blend of four coffee beans with complex aromas and flavors. If you can't find it, a strong French roast is a decent substitution, though the flavor won't be quite the same.
Do not use "sweetened condensed filled milk," made with skim milk and added vegetable oil, in this recipe. Stick to brands that list milk and sugar as the only ingredients.
In a medium heavy-bottomed saucepan, bring half and half just to a boil over high heat. Remove from heat as soon as it begins to boil, then stir in coffee and steep for 4 minutes
Whisk together egg yolks and condensed milk until thoroughly combined in a large bowl. Ladle about 1/3 of half and half into yolk mixture, whisking constantly, until well combined, then slowly transfer back to saucepan, whisking constantly.
Return pan to medium heat and cook, whisking frequently, until a custard coats the back of a spoon and a swiped finger leaves a clean line.
Stir in salt to taste. Pour through a fine mesh strainer (it's okay if some coffee grounds make it through) into an airtight container and refrigerate overnight.
The next day, churn ice cream according to manufacturer's instructions. Chill ice cream in freezer for 3 hours before serving.