Add the egg whites to the bowl of a clean stand mixer, fitted with the whisk attachment. Whisk until frothy; add the cream of tartar. Continue to whisk another 30 seconds. Add the marshmallow fluff and continue whisking for 2 to 3 minutes or until stiff peaks form. It is ready when you have stiff, glossy peaks that hold their shape when the whisk is removed.

Transfer the fluff to a piping bag fitted with a large plain tip. Pipe the fluff around the rim of the mug or glass or on top of the drink itself. To caramelize, apply a kitchen torch a few inches away from the fluff and move it in a quick, sweeping motion across the fluff until the peaks of the fluff caramelize and turn a light brown.