Pre-heat your oven to 325F and line the bottom of 3 9-inch round pans with parchment paper. Do not grease.
In a large bowl, whisk 1 3/4 cups sifted cake flour, 1 1/4 cups granulated sugar, 1/2 cup Dutch processed cocoa powder, 2 teaspoons baking powder, 1/4 teaspoon baking soda and 1/2 teaspoon salt until combined. Set aside.
In a medium bowl, whisk 3/4 cup coffee, 1/2 cup canola oil, 5 egg yolks and 1 teaspoon vanilla extract until smooth and thoroughly incorporated. Add to your flour mixture and whisk until smooth. Set aside.
Using a handheld electric mixer or a stand mixer fitted with the paddle attachment, beat 8 egg whites and 1/2 teaspoon cream of tartar on medium speed until you reach soft peaks. Then switch to high speed and gradually add 1/4 cup sugar. Beat until the egg whites are very stiff and dry - the egg whites should be on the brink of losing their shine.
Fold your egg whites into your batter in thirds. Gently fold until each addition is incorporated.
Transfer the batter equally into your 3 pans and bake for 30 minutes or until the top springs back when lightly pressed and a toothpick inserted in the centre comes out clean.
Run a sharp knife along the sides of each cake and allow to cool in the pan for 10 minutes. Then unmold and transfer to a wire rack to cool completely.
For the Vanilla Whipped Cream Frosting:
Pour 1 packet of unflavoured gelatine into 1/4 cup cold water. Do not stir. Let sit for 10 minutes to allow it to bloom.
In the meantime, using a handheld electric mixer or a stand mixer fitted with the whisk attachment, whip 2 cups heavy cream, 2 tablespoons granulated sugar and 2 teaspoons vanilla paste on medium high speed until you reach soft-medium peaks.
Get your gelatine and microwave in increments of 10 seconds until dissolved. Whisk until smooth and to bring it down to room temperature (it shouldn't be hot to the touch).
Add a dollop of whipped cream to the gelatine and stir to temper it.
Add the tempered gelatine to the rest of your whipped cream. Continue whipping until the gelatine is incorporated and you reach stiff peaks or get the consistency you want.
Chocolate Chiffon Cake Assembly:
Evenly spread a generous helping of whipped cream frosting on top of the first cake layer. Put on the next cake layer and spread more frosting on top of that. Put the last cake layer on and proceed to cover the rest of the cake with whipped cream frosting and decorate as desired.
Chill for at least 3 hours before serving.
Make sure your cakes are completely cool before frosting.