Preheat the oven to 338°F (170 °C).
Prepare a heart-shaped baking form, smear well with melted butter and sprinkle lightly with flour. It needs to be about 8 3/4″ (22 cm) in diameter, 2 1/2″ (6 cm) tall.
Cool the eggs to make it easier to separate the egg whites from the yolks. Use the quantities listed. Cover and leave them for 30 min. at room temperature.
In another bowl, mix together the oil, coffee at room temperature, vanilla.
Beat the yolks with 1/2 cup (135 g) sugar using a mixer. Pour in the oil mixture slowly in a trickle, while beating nonstop on very low speed with the mixer. Add the flour mixture, stir with the whisk. You need to obtain a heavy, shiny, chocolate dough.
Beat the egg whites and lemon juice to a nice, rich white foam. Add 1/5 cup (65 g) sugar and beat to soft but tight peaks. Pour it into the chocolate dough in 3 lots. Stir the dough carefully and slowly to prevent too much air from getting into it.
Pour it into the form. Bake at 338°F (170 °C) about 35-40 min. or to a dry toothpick.
Take the baked cake out of the oven and slide a spatula along its perimeter immediately. Leave it in the form about 15 min., then invert onto a cooking grid. Once it's fully cooled, cut it into 2 separate layers.
In a mixer bowl put 1/2 cup (120 g) cold cream, the sifted cocoa, vanilla and 1 2/3 tbsp (25 g) sugar and beat to stiff peaks.
Distribute the prepared cream over the 1st cake layer.
Beat the remaining cream and sugar and distribute over the 1st. Cover with the 2nd cake layer, pressing lightly. Cover the cake with foil and leave in the fridge for 1 hour.
Break the chocolate into pieces. Heat the cream with the butter. Remove from the stove and pour in the liqueur. Stir and leave in the fridge for 20 min.
Assembling the cake:
Remove the foil from the cake and slide your hands along its sides to get rid of the crumbs still attached after you cut it. Place it onto a cooking grid, place a wide and flat tray under the grid in turn. Pour the ganache right in the middle but let it run along the edges down the outer walls. Slide a wide spatula very carefully on top to distribute the ganache properly.
Leave at room temperature about 15-20 min. for the chocolate to harden, then transfer to a serving plate. Leave it at room temperature for a few hours.
Optionally, from the chocolate that's spilled down into the tray you can form small chocolate balls, roll them in cocoa and arrange on top of the cake.
Notes: If you don't have a cake layer slicer you can cut them with a knife. First measure the height of the cake layer (ex. 1 1/2″ (4 cm)), divide it in 2 and stick toothpicks all around its circumference along the 3/4″ (2 cm) mark. Slide a knife slowly above the toothpicks with a wide and sharp knife. You now have your layers separated.