Heat heavy cream in a saucepan for the chocolate cream.

Add half of the chopped dark chocolate, remove from heat, and let stand for 5 minutes.

Whisk vigorously, then transfer to a clean, dry mixing bowl.

Cover the surface of the cream with plastic wrap and let cool.

Chill the cream for at least 5 hours, or overnight.

For the dulce de leche, cover the unopened can of sweetened condensed milk with plenty of water in a pot.

Simmer for about 2 hours, adding more water as necessary to keep the can covered at all times.

Remove from the water and let cool completely.

Preheat oven to 325°F.

Grease an 8-inch springform pan.

Melt remaining chocolate and let cool.

Whisk 2 egg yolks until creamy, then add sugar, vanilla extract, and a pinch of salt.

Add remaining 4 eggs, one at a time, followed by melted chocolate.

Mix flour, cocoa, and baking powder together and fold into the batter.

Beat egg whites until stiff and fold in.

Transfer to the prepared pan and smooth.

Bake for 50 minutes.

Remove from oven and let cool on a wire rack.

Remove the cake from the pan and cut into 3 layers horizontally.

Spread about 1/3 of the dulce de leche on the bottom layer of cake.

Add the middle cake layer and spread with another 1/3 of the dulce de leche.

Repeat with the top layer.

Whip chocolate cream and brush half over the cake.

Transfer remaining chocolate cream to a piping bag with a large tip and pipe chocolate tufts around the cake.

Chill until ready to serve.

Dust with cocoa powder.