Warm the milk gently. Add the milk to a small saucepan over medium-low heat.
Bring it just to the point of steaming, not boiling.
Bloom the cocoa and spices. Whisk in the cocoa powder, cinnamon, and your chosen chili. Let it warm for 1 minute to bloom the flavors.
Add chocolate and sweetener. Stir in the chopped dark chocolate and sugar or maple syrup. Whisk until the chocolate melts and the mixture looks glossy and smooth.
Season and finish. Add vanilla and a pinch of salt.
Taste and adjust sweetness and heat. If you want it richer, add another small handful of chocolate and whisk until melted.
Heat to your liking. Keep it on low heat for another 1–2 minutes, stirring often. Don’t let it boil.
It should be hot and slightly thick.
Serve. Pour into mugs. Top with whipped cream, a sprinkle of cinnamon, a few chocolate shavings, or a tiny pinch of chili flakes for flair.