Bring a pot of water to a simmer. Over it melt the chocolate in a heatproof bowl, making sure the bowl doesn't touch the water. Once melted, let it cool for a couple of minutes and stir in 4 tablespoons of yogurt.
In another bowl whisk the egg whites until stiff. Add the sugar and whisk until stiff again. Fold a tablespoon of the whites into the chocolate mixture to loosen it up just a bit and then gently fold in the rest. You can add a drop or two of vanilla or rum essence if you prefer.
Pour this mixture in small glasses and refrigerate for a about two hours. Just before serving top each glass with a tablespoon of yogurt and some grated chocolate. Bon appetit!
Recipe by Simply yum at https://www.simplyum.com/sunday-morning-chocolate-mousse/