Create a double boiler by heating a small pot of water until it steams, but kept below the boiling point. Rest a heatproof glass dish on top of that but do not allow the water to actually touch the glass dish.
Place the butter, chocolate and espresso in the bowl and stir about with a rubber spatula until it has melted completely. Remove from the steaming water and set aside to cool. It wouldn’t be a terrible idea to stir it every now and then, too.
While you wait for the chocolate concoction to cool, get on with the rest of the cake. You will need two separate bowls to prepare the eggs in. You cannot beat your yolks in the bowl of your mixer, pour it out and then start in on your egg whites or they will never whip and stiffen. The slightest trace of fat in the bowl, or anything that comes in contact with the whites, and they will give up on whipping for you without second thought.
So, in one bowl, cream your egg yolks, sugar, vanilla and Amaretto until it turns a pale canary yellow and falls from the mixer/beater in a smooth, constant ribbon. Fold in the cooled chocolate-butter mixture, slowly at first, and then almond meal and set aside.
Whip the egg whites in a separate bowl until it forms stiff peaks.
To marry the two, spoon out about a quarter of the whites into the chocolatey yolks. Without any concern for deflating the whites, stir them into the mix. Doing this helps to loosen and aerate the mixture and makes folding, in the truest sense of the word, so much easier.
Once you’ve beaten in the first quarter of the whites, add the rest of the whites to the mix and, with a rubber spatula, fold the whites in gently. The best method to do this is by cutting into the center of bowl on an angle, through the whites and yolks, to the bottom. Scrape the spatula along the bottom and sides of the bowl and in a single motion fold it over the whites. Turn the bowl about a quarter-turn and repeat. Ideally, you’d do this as few times as possible because the more folding you do, the more air you will loose and you want to keep as much air as possible. Since there’s no flour or leaveners you are relying solely on the egg whites to give the cake some bulk and make it rise.
Pour the batter immediately into a greased and sugared 9” spring form pan and bake for 20 – 25 minutes. Keep an eye on it after the 20 minute mark though, as it can start to scorch a little (if it does it’s not the end of the world—you can flake any really dark bits off and cover them up with the cream later). You’ll know it’s done when the edge of the cake pulls away from the sides of the pan just slightly and the center has a slight wobble to it.
Remove the cake from the oven and set on a cooling wrack, in the pan still, to cool completely before retiring it to the fridge. It will get much firmer and denser in the fridge but it does benefit from having a slight chill to it. The cake will fall a moderate amount from the height it had risen to, but this is normal and leads to a much fudgier, chocolatier cake.
Serve with the spiked whipped cream either on the side or covering the top as a whole.
-Check to make sure the chocolate and powdered sugar you're using are gluten free! Some brands do have ingredients that contain gluten so be sure to check the label!
-I like a mix of roughly 10.5oz of 70% cacao and 3.5oz of 85%.
-You can use any liqueur you like here; Cointreau, coffee/espresso liqueur, hazelnut, cherry (like cherry heering or brandy), etc. Dark rum is also good!
-You can make this WAY ahead and freeze it. Just let it get firm and chilled in the fridge before double wrapping it in plastic wrap. Wrap it again in aluminum foil and freeze for up to 3 months. Let it defrost in the fridge for 24 hours before you plan on serving it.