I first saw this on Instagram - here is the link: chocolate mousse - and I had to try it. It sort of worked but I made an error on the ratio of liquid to chocolate. This link gives more information on the science involved: the science.
I used Bakers Unsweetened Chocolate primarily because this is what I had on hand. Research tells me that the higher the cocoa butter content in the chocolate the better the success rate. However, this applies to using water as the liquid.
Wanting a richer mousse I decided to replace the water with my barista style oat milk. The oat milk has elements in it that replace the cocoa butter which may be lacking in the chocolate.
My family does its best to avoid refined sugar. I sweetened the chocolate with maple syrup. I tend to use dark or amber syrup as they are richer in taste but for this recipe that really doesn't matter. Regular maple syrup should work just fine.
One final note: I like to eat my mouse with one of the smallest spoons I own. This allows me to savour each delicious mouthful. I strongly suggest that you use ramekins as opposed to the bowl I used below. It was so rich that I couldn't finish it in one sitting.