This is what I've been looking for too much time: a perfect alternative to the commercial solutions with little or no effort, vegan, dense and good tasting.
Step 1: Gather Ingredients
For a full cup, you'll need:
-cocoa powder 10g
-corn starch 10g
-cane sugar 15g(or less if you use white, refined, unhealthy sugar)
-soy milk 200g(or rice, almond, other veg unsweetened, without added unhealthy things)
Step 2: Mix Everything
First mix cocoa, starch and sugar, then slowly add milk and begin stirring.
Step 3: Microwave Time
This is the critical part: put everything in microwave, 900w for 2 minutes, every 30 sec stop, stir and check, keep an eye on the mug(you don't want to clean everywhere because of milk beginning to overflow, do you?).
Step 4: Magic Happens
When heated, starch thickens, sugar melts, everything is ready to become the Perfect Vegan Hot Chocolate, you can add some cinnamon and veg biscuits or other unhealthy, more classic things like marshmallows, cream etc.