Maybe glaze is the more appropriate term. Or icing. Maybe there’s more than one option. I already told you, I’m not a recreational cook.
The cake I had planned some time ago did not turn out the way the recipe promised, but the chocolate frosting for it was a total success! Which means I felt excited enough to try it again and obviously it can be used for a variety of desserts, for example, a yogurt cake.

If you read in German, there’s a bunch of recipes for chocolate frosting here, or the one I’m about to explain is included here, OR there’s loads right here too. Just to list a few examples.
For the frosting I picked, I liked that it didn’t include tons of butter or sugar. What you will need is:
100 g of what in German is called Schlagsahne, and the dictionary tells me is whipped cream or meringue chantilly in English. Isn’t it fun to decipher all this between languages, dairy products in particular?
1 tsp butter or coconut butter.
The recipe says a whole bar of plain dark chocolate, but I think it’s a bit much based on my first try. Half a bar or a few pieces if it’s a thicker one will do just as well. It’s also fine if it has an additional flavour, like oranges, and I would guess that using milk chocolate would work too.
You pour the cream in to a small pot, break up the chocolate in to small pieces, add those and the butter, then stir everything on low heat until it all melts together. It looks like cocoa first, then darkens and thickens after 20 minutes or so.
Experience shows that there’s more than enough frosting for a bigger cake, so let your baking flag fly.