For seriously gorgeous mousse, you need to cook the creme anglaise (fancy french for egg yolks and cream/milk), add cocoa, other flavour, or essence or both, sweetener of your choice as part of the creme anglaise, pour into serving dish, cool on the bench, put in the fridge for at least four hours. Serve with cream and choc shavings as above. Delish.
I realised this when learning to use my ice cream maker. As the first (and labour-intensive) part of the ice cream making process, I discovered that the pre-putting in the ice cream maker part was actually divine mousse. My fave is stevia sweetened chocolate melted in with the creme anglaise. Seriously chocolate, and great on the BG levels, as in no spiking.
The whisking, cooking on the stove top and additional whisking gives it the right amount of aeration, if that is the word, the right chemistry between the sweetener if using, the flavours, and the egg yolks as in binding, that gives mousse its hallmark creamy smooth melt-in-your mouth texture.