Is it possible to effectively dissolve chocolate into coffee?

As you already observed fat and water separate from each other. In this regards your coffee-choclate-mixture is similar to a salat dressing made from vinegar and oil, you can mix it but after some time the both parts will separate from each other again.

To create a stable fat-water-mixture you will have to add an emulsifier like soy lecithine. As an alternative you could try to blend in an egg yolk which is the traditional source for lecithine in ice cream making, in this case you have to take care that the temperature is kept below 65°C to ensure the yolk does not cook. Because this also means it is not pasteurized you should only use very fresh eggs for this purpose and take care the yolk does not get into contact with the outside shell.

If convenience is your priority, then making an emulsion might not be the best solution. I would recommend making a chocolate syrup to mix into your coffee. A recipe based on water or milk with cocoa powder rather than chocolate will produce the best result mixed into coffee. Using a good quality cocoa powder will produce a very tasty result. Most coffee shops use a chocolate syrup to produce their mocha coffees because they incorporate so much easier than pure chocolate.

I am not understanding the amount of time and extremes for answers. I get in kicks where I melt chocolate into my coffee for a day or two a week to mix it up (I am a pot a day minimum person).

1. Chop up part of bar.
2. Put it in microwave at 20% power in your coffee cup.
3. 15 seconds.
4. Check it out.
5. It should be slightly melted - let the coffee do the rest. For some type of chocolates I have had to put a wet paper towel on top and add time in the microwave.
6. Pour coffee.
7. Stir.

As mentioned every chocolate will have specifics. If you do about the same amount, with same chocolate, this should add no more than 30-40 seconds to your day and without adding ingredients you are getting the chocolate flavor, not a sugary taste (which I do not like as I drink my coffee black or just a bit of chocolate). The chocolate powders or emulsions or hot cocoa powder may taste good or better to some but this is different from your description and is a sweeter cup.

If you are not watching calories, and want a treat, use good quality chocolate ice cream. Add a shot or two of espresso, stir, add milk to taste. The result is a very rich chilled mocha drink.

If you have a small smoothie blender, try zerping the coffee + chocolate while it’s hot just before drinking. It might stay emulsified for long enough.

Not sure where you are from, but in germany we have "Pocket Coffee" from Ferrero, they just fill a chocolate piece with coffee. This way you still have the chocolate melting part before you get to the coffee.

Hervé This, the French physical chemist focusing on molecular gastronomy discovered how to create a mousse from chocolate and water/liquid.

"I invented chocolate Chantilly — how to make a chocolate mousse without eggs, just foaming the chocolate. I was very proud, I got prizes for that. Later I discovered you can make the same with butter, foie gras, or even olive oil, so the invention is nothing [big in itself]."

Chocolate chantilly

• 200ml water
• 225g bitter chocolate (with a high percentage of cocoa butter)

Melt the chocolate in the water over medium heat. Stir until smooth. This forms a mixture where the cocoa butter can be mixed like cream. Pour the chocolate into a bowl cooled by an outer bowl of ice and water. Whisk until whipped.

You can flavor the water with anything so coffee, or a liquor.

I have followed this recipe before, it turns out quite strong if you use a bitter chocolate (for my taste).

Note: Three things can go wrong. Here's how to fix them. If your chocolate doesn't contain enough fat, melt the mixture again, add some chocolate, and then whisk it again. If the mousse is not light enough, melt the mixture again, add some water, and whisk it once more. If you whisk it too much, so that it becomes grainy, this means that the foam has turned into an emulsion. In that case simply melt the mixture and whisk it again, adding nothing.

https://food52.com/recipes/16044-herve-this-chocolate-mousse https://www.nature.com/articles/news.2008.689/box/1

I do this every day, though I don't use chocolate bars. I have tried every brand of spicy hot cocoa mix on the market that I could find and my favorite for both flavor - and how well it dissolves in my coffee - is Equal Exchange Organic Spicy Hot Cocoa. I absolutely love the stuff. A lot of other brands did not dissolve as well. Equal Exchange also has regular and dark versions without the spice.

However, if you prefer to use solid chocolate it is possible with the right mixing method. There is an amazing device out of the UK called the "Hot Chocolate Shaker", made by The Chocolate Society. I purchased it from the original kickstarter - a bit skeptical but hopeful. I was not disappointed. At first it seams rather simple - a cup with a lid for shaking hot cocoa. The magic is in the lid - it starts collapsed and pops out as you shake the hot cocoa. Smoothest hot cocoa ever - whether you use mix or chocolate drops. For coffee, just pour the coffee in, add some chocolate drops, and shake.

Enjoy!