01 - Combine whole milk, heavy cream, half the sugar, and salt in a medium saucepan. Heat over medium heat until steaming, but do not boil.
02 - Whisk egg yolks with remaining sugar in a separate bowl until mixture becomes pale and thickened.
03 - Slowly pour approximately 1 cup of the hot milk mixture into yolks while whisking constantly to prevent curdling.
04 - Return yolk mixture to saucepan. Cook over medium-low heat, stirring continuously with wooden spoon until custard thickens and coats spoon back (170–175°F), approximately 4–6 minutes.
05 - Remove from heat. Stir in brewed coffee, espresso powder if using, and sweetened condensed milk until completely blended.
06 - Pour custard through fine-mesh sieve into clean bowl. Cool to room temperature, then cover and refrigerate until thoroughly chilled, minimum 4 hours or overnight.
07 - Process chilled custard in ice cream maker according to manufacturer instructions until consistency reaches soft-serve stage.
08 - Transfer churned ice cream to airtight container. Freeze for minimum 2 hours before serving to achieve firmer texture.