5 ounces good quality, dark, semi-sweet cooking chocolate
1/2 cup very soft unsalted butter
1/2 cup sugar
3 eggs, separated and at room temperature
3/4 cup almond meal (finely ground almonds)
1/2 cup cake flour
Begin by seperatng the eggs, placing the whites in a spotless mixing bowl. Leave them out at room temperature for 30 minutes.
Prepare a small (8 inch) cake pan by greasing and then lining it with baking paper to insure a good release. Preheat oven to 350°F (180°C).
Using a double boiler arrangement, melt the chocolate over simmering water.
In a mixing bowl, cream the butter and sugar together with a wooden spoon until well combined and fluffy. Beat the egg yolks into the butter and sugar, then stir in the almond meal, the flour and the melted chocolate until everything is well combined.
Using a stand or hand mixer, beat the egg whites until stiff peaks form. Stir 1/4 of the beaten egg whites into the cake batter to lighten it up some, then carefully fold the rest into the batter. The batter is quite stiff so this can be difficult - don't worry, just do your best to not massacre the egg whites. Fold them in just enough to get a homogenous batter.
Scrape and push the batter evenly into the prepared pan and bake for 20 minutes. Remove from oven and let cool for 10 minutes, then turn out onto a rack to finish cooling.