With the rack in the middle position, preheat the oven to 350°F (180°C). Butter and line the bottom of an 8-inch (20 cm) springform pan with parchment paper.
In a bowl, combine the flour, cocoa powder, baking soda and baking powder. Set aside.
In another bowl, combine the eggs, sugar, oil and vanilla with a whisk. Stir in the dry ingredients alternately with the buttermilk until smooth. Spoon into the prepared pan.
Bake for 45 minutes or until a toothpick inserted into the centre of the cake comes out clean. Let cool completely on a wire rack before unmoulding.
Caramel Whipped Cream
In a small bowl, sprinkle the gelatin over 2 tbsp (30 ml) of the water and let bloom for 5 minutes.
In a saucepan over high heat, dissolve the sugar in the remaining water (3 tbsp/45 ml). Cook without stirring until the caramel becomes amber in colour.
Remove from the heat and add ½ cup (125 ml) of the cream. Beware of splattering. Bring the mixture to a simmer, stirring constantly, until smooth. Add the gelatin and stir until dissolved. Remove from the heat. Add the remaining cream (1 ½ cups/375 ml) and stir well.
Strain and cover with plastic wrap directly on the surface of the caramel cream. Refrigerate for 8 hours or overnight (see note).
When ready to assemble, prepare the ganache
Place the chocolate in a bowl. Set aside.
In a saucepan or in the microwave oven, bring the cream to a boil. Remove from the heat and pour over the chocolate. Let melt for 1 minute without stirring.
With a spatula, stir until the ganache is smooth. Cover and let rest for 20 minutes at room temperature or until the ganache has cooled but is still pourable.
Cut the cake horizontally to obtain 2 slices. Place on a baking sheet lined with parchment paper.
Whip the cold caramel cream with an electric mixer until firm peaks form. Spoon the caramel whipped cream into a pastry bag fitted with a plain round tip.
Quickly pipe caramel whipped cream teardrops over both slices of cake, just short of the edge (see note). Refrigerate for 15 minutes or until the whipped cream sets.
Drizzle ½ cup (125 ml) of the cooled ganache over the bottom slice. Place the bottom slice on a serving platter. Delicately cover with the top slice. Drizzle the remaining ganache over the cake, letting it run over the sides. Refrigerate at least 1 hour.
Top with the chocolate curls. Let the cake rest at room temperature just before serving.
The caramel cream requires at least 8 hours of cooling time in the refrigerator in order to be firm enough to whip.
The caramel whipped cream may soften while in the pastry bag. Therefore, we recommend working with it quickly.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.