2) Meanwhile, spoon the cocoa powder into a measuring cup. Once you see little bubbles forming around the perimeter of the saucepan, the milk is hot; turn off the heat. Pour a little milk, about 230ml, into the cocoa powder and whisk until smooth. Add back to the saucepan and whisk in the honey and salt. Stir until well combined.
Pour the hot chocolate through a strainer into four individual mugs and top with marshmallows, if you like.