Preheat your oven to 350°F. Assemble your ingredients as well as a 9x13” pan. ⭐️Do NOT grease the pan and do NOT use a pan with a non-stick coating. Because this is a chiffon cake, it needs to stick to the pan in order to rise properly.

Combine the dry ingredients (flours, salt, baking powder) and sift to remove any lumps. Set aside.

Separate the eggs. To ensure I don’t get any yolks in my egg whites, I crack the eggs one at a time into a small bowl and then transfer the white into a larger bowl. Allow the egg whites to warm to room temperature if they aren’t there already.

To the yolks, add 1 cup sugar and beat with a hand mixer at medium high speed until fluffy and light yellow (about 1 or 2 minutes). Add the milk and vanilla and beat for 30 or 45 seconds to incorporate everything well. Set aside.

With clean beaters, beat the egg whites on medium-high speed for about 1 minute until they are frothy. Add the cream of tartar and beat on high speed for another minute to incorporate it. Then, add the 1/4 cup sugar a little at a time while beating constantly. Continue beating until the egg whites form stiff peaks. Do not overbeat, or else the egg whites may end up too dry.

Make a well in the dry ingredients, and pour in the liquid egg yolk mixture. Stir just until everything is well mixed. The batter will be fairly thick and sticky.

Add half the egg whites and then gently fold them in until no white streaks remain.

Add the remaining half of the egg whites, and repeat the folding process. ⭐️ The egg whites are what gives this cake most of its fluffy texture. You don’t want to be too rough during this step, because if you knock all of the air out of the whites, the cake will not rise.

Gently pour the batter into the ungreased 9 x 13“ pan. Gently spread the batter so that it is evenly distributed in the pan.

Place in to the preheated oven, and bake at 350°F for 20 to 25 minutes. An inserted toothpick should test clean.

Remove the cake from the oven, and place it upside down on a cooling rack. This will help prevent the cake from shrinking/falling and becoming dense. Another good way to prevent the cake from losing its fluffy texture is to soak a kitchen towel in cold water, wring it out, and place it over the bottom of the pan. This will help draw away the heat quickly. The faster the cake cools, the less of a chance it will have to shrink.

While the cake cools, make the milk mixture. Combine all of the milks in a bowl, and beat them for about 45 seconds to fully incorporate them.

When the cake is only very slightly warm to the touch, run a knife around the outside edge of the cake to loosen it from the pan. Then, using a skewer, poke holes over the surface of the cake. (I tried using a fork to poke holes, but tore the surface of the cake too much, so I resorted to using a toothpick as well as a thin chopstick.)

Pour the milk mixture over the cake. Cover the cake and place it in the refrigerator for at least one hour. Ideally, an overnight soak is best.

The next day, make the whipped cream topping by combining the heavy whipping cream and powdered sugar in a large bowl. Beat on high speed until the cream forms peaks. Be careful not to overbeat, or the cream will turn into butter!

Slather the whipped cream over the cake and swirl with the back of a spoon. If desired, sprinkle with a little bit of cinnamon.

Slice and serve as is, or add your choice of fresh fruit. Store any leftover cake in the refrigerator for up to four days.