Coffee Ice Cream

In a 2 to 3-quart saucepan over medium heat, warm the half-and-half and corn syrup until steam begins to rise from the surface, 3 to 4 minutes. Remove from the heat.

In a heatproof mixing bowl, whisk together the egg yolks, sugar and salt until blended. Form a kitchen towel into a ring and place the bowl on top to prevent it from moving. Gradually add the hot half-and-half mixture, whisking constantly until fully incorporated. Return the mixture to the saucepan and place over medium-low heat. Cook, stirring slowly and continuously with a wooden spoon or spatula, until the custard thickens and a finger drawn across the back of the spoon leaves a path, 8 to 10 minutes; do not allow the custard to boil.

Pour the custard through a fine-mesh sieve set over a clean bowl and stir in the coffee extract. Nestle the bowl in a larger one filled halfway with ice and water and cool the custard to room temperature, stirring occasionally. Refrigerate until chilled, at least 1 hour.

Transfer the custard to an ice cream maker and freeze according to the manufacturer's instructions. Transfer the ice cream to a chilled container, cover and freeze until firm, 3 to 4 hours.