Use an electric mixer, a KitchenAid, with the whisk attachment at high speed to mix the ingredients evenly;
Beat the eggs and ½ of the sugar for 10-15 minutes until light in color and fluffy;
Melt the chocolate in a heatproof bowl over a saucepan of simmering water or in a double boiler. If you want to save time, melt it in the microwave, but only in 20 seconds intervals to keep it from burning. Add the oil and stir well to combine. Set aside to cool;
Pulse the almonds with the remaining sugar until it forms a coarse, sand-like mixture;
Turn off the mixer and add the almond and sugar mixture, the cocoa powder, the melted chocolate, the oil, and the rum. Add these ingredients a little at a time and in this order;
Butter a round 9-inch (24cm) baking pan and pour in the cake batter;
Pre-heat the static oven to 425°F (200°C) and bake for about 10 minutes. Then decrease it to 350°F (180°C) and bake for about 20-25 minutes. Hint: don’t use a convection oven as it dries the core of the cake out too much. Insert a toothpick into the middle. It should come out with a few moist crumbs in order to retain its moist consistency;
Take it out of the oven and allow to cool for about 30-40 minutes on a wire rack. The cooling time is very important because the cake must be completely cold before turning it upside down; otherwise, it could break. Turn it upside down and remove it from the baking pan. Dust it with powdered sugar.