Brew your coffee: Pull a shot of espresso or brew very strong coffee. Keep it hot while you make the chocolate orange milk.
Warm the milk base: In a small saucepan over low heat, add milk, chocolate chips, cocoa powder, sweetener, and a pinch of salt.
Whisk constantly until the chocolate melts and the mixture is smooth and steamy, about 3–4 minutes. Do not boil.
Add citrus and vanilla: Stir in the orange zest and vanilla. Keep on low heat for 30–60 seconds to infuse the flavor, whisking gently.
Froth (if you like): Use a handheld frother, whisk briskly, or shake the hot mixture in a heat-safe jar with the lid slightly vented to create foam.
Aim for a silky texture.
Assemble: Pour the espresso into a mug. Top with the chocolate orange milk, holding back some foam with a spoon, then spoon the foam on top.
Finish: Taste and adjust sweetness. Garnish with a little extra orange zest or shaved chocolate if you want a café look.