This is not a light and fluffy cake. It has heft. Just saying. Because of the heft, you don't need much...
ground almonds (almond flour)
dark chocolate, grated
2 drops almond extract
pinch cream of tartar
In a Bowl 1 mix the almond flour, grated chocolate, cinnamon and salt. In Bowl 2 cream the butter and the sugar well, and add the essences. In Bowl 3 whip the egg whites until soft peaks form. Add the cream of tartar and whip once or twice more.
To the creamed butter add the egg yolks one by one until well mixed-in. Now begin to pour the dry mix of almonds and chocolate into the butter and egg batter. Keep stirring - it becomes quite thick. Slide in half the egg whites and fold them through the thick batter. This helps to break it up. When they have been smoothly incorporated, add the rest of the whites gently, folding them in again.
Pour into a greased and lined spring form pan or quiche dish. If you don't line the dish with buttered parchment the tart will stick to the bottom. If it's a quiche dish just lay a big piece of parchment over the dish, butter it, and pour the batter in, nudging it to the edges so that the paper is cozy with the sides of the dish, all the way around
Bake at 350'F/180 C for about 25 minute until just set.
When cooked and cooled, slide a knife around the edges and lift the tart out, parchment and all. Peel the paper off and return the tart to its dish, or to a pretty plate.