I take a few spoonfuls of cocoa powder, add a few spoonfuls of sugar, and vigorously mix in a very small amount of milk. Very soon (and with no cooking involved), I have a very, very chocolatey pudding-mousse-like substance that is very, very tasty (if you like chocolate). I’ll eat this with a spoon, or mix it into a full glass of milk to make very good chocolate milk.
You can also use whipped cream.
I don’t do it, but it sounds like one of the recipes in the can of cocoa powder I bought in the UK. Don’t have it here or I’d copy it (I don’t remember the brand either). Both the usage and what I remember of the recipe match.
I’ll have to try that. My own use of cocoa is a half of everything mocha: half a teaspoon of cocoa, half a teaspoon of brown sugar, half a teaspoon of coffee, half a cup of hot water and half a cup of milk.
Add a little more milk and heat it, and that’s how I make hot cocoa. Hate mixes. Barely use any sugar.
I don’t eat it straight, but I do use it as a base for hot cocoa and chocolate milk. I also add a pinch of salt and a few drops of vanilla and sometimes a pinch of cinnamon, and instead of milk I use half-and-half or cream for the base, to which I add milk.
Also when I said I don’t eat it straight I was lying, because when you make it for chocolate milk and hot cocoa you kinda gotta eat a bit before you add the milk.
I’ll bet RangerJeff has made pudding like that from MREs. 
This is basically how I make chocolate milk when we have cocoa powder and no Quik.
Another way to make quasi-mousse is small box of Jell-O Heat & Serve pudding, 1¼ cups milk, and 8 oz. Cool Whip (or a large box and double the milk & Whip). Mix together, heat according to instructions on the Jell-O box, and cool in the fridge overnight.
Accidentally discovered this when trying to make frosting.
When I want to do something quick I stir it into a carton of thawed no-fat Cool Whip. No added sugar necessary. And then I use it as a filling for cream puffs.
Or you can stir it into your meringue recipe and make little shells, bake them and serve them filled with ice cream, drizzled with hot fudge sauce and topped with whipped cream. Looks all ritzy-ditzy but is easy.
The only thing I do with cocoa powder is add a heaping tablespoon of it whenever I make a pot of chili.
Mixing the sugar and coco, then a little milk is a good way to start chocolate milk or hot chocolate so it mixes good. Otherwise coco likes to lump.
You need to look up a simple recipe for ganache. Be prepared to go nuts.
I used to make a pseudo cookie from an old pie shell recipe - basically flour, butter, salt, and water. I added sugar for the cookies. After a while, I started adding cocoa too for the “chocolate” version. It’s pretty easy to make with ingredients on hand, at least for my kitchen.