Making my cocoa mix into instant cocoa mix
Looking at the ingredients for Nesquick for example:


SUGAR
COCOA PROCESSED WITH ALKALI
SOY LECITHIN
CARRAGEENAN
SALT
ARTIFICIAL FLAVORS
SPICE
VITAMINS AND MINERALS: CALCIUM CARBONATE, ASCORBIC ACID (VITAMIN C), ZINC OXIDE, PYRIDOXINE HYDROCHLORIDE (VITAMIN B6), COPPER GLUCONATE, MANGANESE SULFATE, BIOTIN.


The key elements are soy lecithin, which is an emulsifier, and carrageenan, which is a thickener especially effective in dairy products.  The lecithin will help the cocoa to become suspended in the liquid phase, and the carrageenan will help the particles not stick to each other.

What does not appear on the label is how some of these ingredients are processed.  It is likely that the cocoa is modified by being pre-gelatinized, so that  it will have reduced clumping properties, and then reground quite fine to enhance how well it dissolves.  This is not something that you can achieve at home.



As you mention, you can probably create a syrup from your ingredients, but it may settle over time and have to be shaken.