In a small saucepan off heat, whisk cocoa powder with 2–3 tablespoons of the milk and your sweetener until smooth. This prevents lumps and sets you up for velvet, not chalk.
Pour in the remaining milk and a pinch of salt. Set over medium-low heat, whisking frequently until steaming and hot but not boiling (tiny bubbles at the edges). Boiling can dull flavor and form a skin—no thanks.
Remove from heat. Stir in vanilla and any spices. For a café feel, blend with an immersion blender for 10–15 seconds or whisk vigorously to create microfoam.
Sip carefully and adjust sweetness or cocoa to your preference. If it's too intense, add a splash more milk; too mild, dust in 1/2 teaspoon cocoa and whisk.
Pour into a pre-warmed mug. Optional: a dollop of whipped cream, a sprinkle of cocoa, or a cinnamon dash. Cozy mode: activated.