Yesterday I made this cake with a recipe from Donal Skehan. It's a gluten free cake though I don't have any problem with gluten anyway. For the cake you only need dark chocolate, butter, sugar, ground almonds, eggs and Frangelico. For the chocolate drizzle, dark chocolate, butter, double cream, sugar and chopped hazelnut.
I think the thing that needs a bit more attention was the egg whites; make sure they're thoroughly whisked til stiff edges appear, therefore the cake will rise nicely and the texture will be delightfully moist. When I read the recipe and found no flour or baking powder, I was afraid that the texture will be dry like those microwave made instant chocolate cake. I was wrong, of course :) It was so fluffy *despicable me reference*
Adding toasted hazelnut on top made the middle part tasted a Nutella-ish (which I love). I think I should've baked it a little longer so the middle of the cake won't still be soft and dough-y, but I'm not too sure because I actually love it this way, a little like chocolate lava cake. And I'm thinking about adding more Frangelico so it'd be more apparent on the taste.
I think I'd surely make this cake again. <3