Preheat your oven to 350°F / 175°C.
Grease and flour two 8-inch or 9-inch round cake pans.
In a large bowl, place the finely minced vanilla bean and cover with the boiling water.
Let it steep for at least 5-10 minutes while you gather the other .
In a separate medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Set aside.
In another clean, dry bowl, use an electric mixer to beat the egg whites on high speed until stiff peaks form. Be careful not to overbeat.
To the bowl with the steeped vanilla and water, add the egg yolks, sugar, oil, and vanilla extract.
Beat with the electric mixer until the mixture is creamy, bubbly, and light in color.
Add the dry to the wet and mix on low speed until just combined and smooth.
Do not overmix.
Gently fold the beaten egg whites into the chocolate batter in three additions using a spatula. Be thorough but gentle to maintain the airiness of the whites.
Divide the batter evenly between the two prepared cake pans.
Bake for 20 to 25 minutes, or until a toothpick inserted into the center comes out clean.
Let the cakes cool in their pans for 10 minutes before carefully inverting them onto a wire rack to cool completely.
Once cool, frost the first layer, add an optional jam filling, place the second layer on top, and frost the top and sides.
When folding in the egg whites, use a light hand. The goal is to incorporate them without deflating the air you just whipped in. This is key to the cake's tender crumb.
Do not overbake.
Check the cake at the 20-minute mark. A moist crumb is what you're looking for, so pull it from the oven as soon as a toothpick comes out clean or with a few moist crumbs attached.
