01 - Combine whole milk, heavy cream, half the sugar, and salt in a medium saucepan. Heat over medium heat until just steaming, being careful not to boil the mixture.
02 - Whisk egg yolks with remaining sugar in a separate bowl until the mixture becomes pale and thick in texture.
03 - Slowly pour approximately 1 cup of hot milk mixture into the yolks while whisking constantly to gradually raise the temperature without curdling.
04 - Return the yolk mixture to the saucepan. Cook over medium-low heat, stirring continuously with a wooden spoon until the custard thickens and coats the back of the spoon, reaching 170–175°F, approximately 4–6 minutes.
05 - Remove from heat and stir in brewed coffee, instant espresso powder if using, and sweetened condensed milk until completely blended.
06 - Pour the custard through a fine-mesh sieve into a clean bowl. Allow to cool to room temperature, then cover and refrigerate until thoroughly chilled, minimum 4 hours or preferably overnight.
07 - Process the chilled custard in an ice cream maker according to the manufacturer's instructions until the desired consistency is achieved.
08 - Transfer the churned ice cream to an airtight container and freeze for at least 2 hours before serving to achieve a firmer, scoopable texture.