Line the bottom and sides of an 8-inch springform pan with parchment paper. Preheat oven to 350℉ (177℃).
Melt ½ cup of oil and semisweet chocolate pieces over low heat. Remove from heat when they are just soft enough to be whisked smooth. Allow to cool a little.
Meanwhile, separate eggs by putting whites into a large mixing bowl and the yolks into a medium one. *see note below
Whisk egg yolks together with sugar until smooth. Stir in the cocoa powder. Slowly add the melted oil and chocolate mixture. Beat until well combined.
Beat the egg whites until stiff.
Stir ¼ of beaten egg whites into the chocolate-egg yolk mixture. Then gently fold in remaining whites, being careful not to mix more than necessary. Carefully pour into prepared pan.
Bake for 40 minutes or until the center is set. The internal temperature should be 200 ℉ (93℃). Allow to cool in the pan before removing the sides of the pan and serving.
Sprinkle cooled cake with a little coconut milk powder, if desired.
Video
Notes
*I recommend separating your eggs one by one, putting each egg white into a small bowl before adding it to the mixing bowl. If any yolk accidentally gets into your egg whites, they won't beat properly. If an accident should happen and you get a little yolk in with one egg white, you can just put it away for scrambled eggs or some other use later.