Prep Your Equipment: If using a freeze-first bowl attachment, make sure it’s frozen solid—at least 16 hours ahead. It should feel like a frosty brick and make no sloshing sounds when shaken.

Make the Custard Base: In a medium saucepan, combine the milk and cream. Warm over medium heat until steaming (not boiling). In a separate bowl, whisk the egg yolks and sugar until pale and slightly thickened. Temper the yolks by slowly whisking in about 1 cup of the hot milk-cream mixture. Pour this back into the saucepan and cook over medium heat, stirring constantly, until the mixture thickens slightly and reaches 170–175°F (it should coat the back of a spoon). Remove from heat. Stir in the espresso, vanilla, salt, and (if using) coffee liqueur.

Strain & Chill: Strain the custard through a fine-mesh sieve into a large bowl or spouted measuring cup. Let it cool to room temperature, then cover and refrigerate until fully chilled—at least 4 hours or overnight.

Churn the Ice Cream: Attach the frozen bowl to your mixer and churn the cold base for 20–30 minutes, until it reaches a soft-serve consistency.

Make the Espresso-Chocolate Swirl: Place the chopped chocolate in a heatproof bowl. Pour the hot espresso over it and stir until fully melted and smooth. Let cool slightly until warm (not hot).

Swirl & Layer: Transfer half of the churned ice cream into a storage container. Drizzle a few ribbons of the espresso-chocolate swirl over it. Let it begin to set (about 5–10 seconds), then gently swirl it in with a spatula or butter knife. Repeat with remaining ice cream and more swirl. Add any mix-ins between layers if using.

Freeze to Set: Press plastic wrap directly onto the surface of the ice cream and freeze for at least 4 hours, or until firm and scoopable.

Serve (Affogato-Style): Scoop into chilled bowls and pour a fresh shot of hot espresso over each serving. Garnish with flaky salt, cacao nibs, or shaved chocolate if desired.