Preheat oven to 180°C. Grease two 9-inch cake pans, line with parchment paper, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans.

Make the cake: Whisk the flour, corn starch, baking soda, cocoa powder, and salt together in a large bowl. Set aside.

Beat the butter and sugar together on medium-high speed until combined, about 1 minute. Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed. Add the oil, egg yolks, vanilla extract, and vinegar and beat on high for 2 minutes. (Set the egg whites aside.) Scrape down the sides and up the bottom of the bowl with a rubber spatula as needed.

With the mixer on low speed, add the dry ingredients in 2-3 additions alternating with the milk and vinegar. Beat in your desired amount of food coloring just until combined. I use 1-2 teaspoons gel food coloring. Vigorously whisk or beat the 3-4 egg whites on high speed until fluffy peaks form for about 3 minutes. Gently fold into cake batter. The batter will be silky and slightly thick.

Divide batter between cake pans. Bake for 30-32 minutes (177°)or until the tops of the cakes spring back when gently touched and a toothpick inserted in the center comes out clean. If the cakes need a little longer as determined by wet crumbs on the toothpick, bake for longer. However, careful not to overbake as the cakes may dry out. Remove cakes from the oven and cool completely in the pans set on a wire rack. The cakes must be completely cool before frosting and assembling.

Make the frosting: Beat the room temperature butter with a hand mixer until smooth, fluffy and until colour changes. Gradually beat in icing sugar until fully incorporated. Beat in vanilla extract.

Pour in milk and beat for an additional 3-4 minutes. Add food colouring, if using, and beat for thirty seconds until smooth or until desired colour is reached.