As someone who champions simplicity in cooking, I have a pretty convoluted way of making hot chocolates. It didn't start out as the mess of labware and coffee equipment, but over the years, I gradually added steps using things I already owned. But at the heart of the recipe have always been two rules: Use good milk and don't burn it. I've always been a fan of heating up the milk rather than pouring cold milk onto boiling water: Nobody likes a watery hot chocolate.
Whilst you could just load up the sugar, I prefer to keep the milk sweet by keeping it under 70°C. The easiest way to keep your milk from burning is to use a thermometer, and when I found out that my old thermometer fit perfectly into one of my little erlenmeyer flasks, I thought it was a pretty perfect match— I'm not saying you should buy a flask just for this purpose (buy one because they make great cocktail shakers, tea kettles, and oil infusers), a milk pan or any small saucepan will do.
Whilst bringing the milk to 65°C over medium heat on my smallest element, I boil the kettle and scoop two teaspoons of dutch processed cacao powder and two teaspoons of raw sugar into a mug. I pour about 30ml of water into the mug and stir the sugar, and cacao into a syrup.
This next step is entirely optional, but to get a layer of froth I foam up the milk in my french press and then use a milk jug to pour a little heart. Since the milk is only 65°C it's important not to lose any more heat, so use some of the remaining water from the boiled kettle to preheat the french press and the milk jug. If this seems like too much effort, just pour your hot milk straight into your mug.
A cool alternative to this last step is to top the hot chocolate with whipped cream, and grate a piece of chocolate over it.
250ml Bannister Downs Full Cream Milk
2tsp Dutch processed Cacao
2tsp Raw Sugar
1oz boiling water
Heat milk on medium-low to 65°C
Mix cacao, sugar and boiling water in cup
Pour milk into the cup, stir slightly to incorporate.