In Luxembourg all pastry shops sell moelleux au chocolat, which looks like to me as chocolate soufflé.
I found the recipe of moelleux au chocolat here. It seems indeed that the ingredients are very similar to that of the soufflé. The only difference is that you do not whisk the egg whites separately.
It takes 20 minutes to prepare the dough and another 20 minutes to bake it. So it is a fairly quick pastry. The only thing I changed is the amount of sugar i.e. exchanging the packet of vanilla sugar to vanilla extract.
INGREDIENTS (for 6 servings)
200 g dark chocolate
175 g butter
250 g sugar
100 g pastry or all-purpose flour
1 teaspoon vanilla extract
Melt butter on a low heat (4 out of 9 grades) and add the chocolate. In a separate bowl whisk together the sugar, the vanilla extract and the eggs. Gradually add the flour to the eggs. Finally, pour the melted chocolate and butter on the mixture.
Grease the oven pan / cake pan with butter and sprinkle it with flour to cover the whole pan; even the sides.
Preheat the oven to 200 degrees (390 Fahrenheit) and bake it until 15-20 minutes. The cake will rise, but don’t worry after you take it out it will fall back. The cake is very soft and inside it is more pudding-like than cake-like. :))) Serve it with vanilla ice cream or whipped cream or vanilla custard.