I have tried making hot cocoa with melted chocolate. Here is how I did it:  Heat up some milk in a mug until it is hot(ceramic tends to do better in microwaves than glass does because it doesn't conduct heat as well as glass does.)  Put half milk chocolate and half dark chocolate(I was trying to go for that bittersweet and semisweet chocolate by using milk chocolate and dark chocolate) in a small thin glass container and melt it completely(not to the point of separation though)  Put a little bit of the hot milk in the chocolate to temper it(same way you temper eggs).  Stir the chocolate into the milk. Now this chocolate was hershey's brand and I used 4 pieces of the milk chocolate and 4 pieces of the dark chocolate.  Keep stirring until it is the same color as chocolate milk or darker.  Now doing it this way I thought "Milk has fat and water and chocolate has water soluble components and fat soluble components so it should be all good with no separation.  However it did separate and there was a little bit(about an 1/8 of an inch of cocoa butter at the top.  However you can't homogenize chocolate like you can homogenize milk.  Now my thought on why it didn't work is because I used 2% reduced fat milk(which means fat is reduced by 2 percent not to 2%) and so there was too little fat.  Even though it was only reduced by a little in terms of fat content, that little bit it was reduced by might be important to prevent separation. However I didn't want to go with organic milk because I know that organic milk separates into water and cream.  So if I want to make hot cocoa using chocolate or make chocolate milk should I go with whole milk and melt the chocolate over the milk in a double boiler or what? 
To answer you points:     However I didn't want to go with organic milk because I know that organic milk separates into water and cream.   If the milk is homogenized, it would be incredibly difficult to separate the cream and skim in your kitchen. Organic has nothing to do with separation, only husbandry practices (cow raising, feed, and lack of antibiotics.)      Milk has fat and water and chocolate has water soluble components and fat soluble components so it should be all good with no separation.   You are correct that both milk and chocolate have fat at water soluble components. However, you are making the assumptions about emulsions that are not true. In chocolate milk you are making an oil water emulsion, meaning you want the fats suspended in the water without aggregating. There are a few ways to do this:   Reduce the particle size so that they cannot physically aggregate in a short timeframe. Add chemical elements which adhere to the fats and halt their aggregation. (This is what lecithin and stabilizers are).   The final way is to force the emulsion through stirring, which will force fat into the mixture. This is the traditional method of chocolate milk making.     Put a little bit of the hot milk in the chocolate to temper it (same way you temper eggs).   Tempering in eggs means to mix two liquids at different temperatures. The reason you temper eggs is to make sure your eggs don't cook, which doesn't apply in this scenario. Tempering chocolate means something completely different. It refers to setting a crystalline solid form in the cocoa butter. 