Back away from the cocoa powder. It's only bringing you down.
Does this look like something you might be interested in drinking? If so, read on! If not, go make yourself a cup of Swiss Miss.
Source: alimentageuse.com
Use solid chocolate, NOT cocoa powder.
This is the most important thing to do. It's how you end up with something creamy and beautiful instead of disappointing and gritty and chalky. It's why the hot chocolate in Europe tastes like love and happiness.
Source: theroadforks.com
Because you want it to look like this:
Photo from this excellent step-by-step recipe at Baked Bree.
Source: bakedbree.com
Instead of this:
Say no to clumps.
Source: vimandverve.blogspot.com