If you enjoy the aromatic spices and deep caramel flavor of Lotus Biscoff cookies, you will enjoy this soft and fluffy chiffon cake infused with Biscoff flavors and biting into little bits of Biscoff cookies at the same time. So good!
Arrange few pieces of Biscoff cookies inside the tube pan. I only put three, I should have put maybe 4 or 5. You can arrange it any way you want it. This will be the top of the cake later when you invert the pan
Prepare the cake batter:
Preheat your oven to 330 F (165 C). If you have a convection oven, I suggest lowering the temperature by 20 F (15 C). Place the oven rack 3rd from the top. Whisk the cake flour, baking powder, and salt to combine. Put 100 gr of Biscoff in a food processor and process into a fine powder. Then crush another 50 grams of Biscoff cookies into smaller pieces. It's nice to bite into tiny pieces of Biscoff in the cake. You can skip this if you don't want to. Set aside
Place the egg yolks, milk, oil, and vanilla extract in a mixing bowl and whisk until combined. Sift in the cake flour mixture and then add the Biscoff powder. Whisk to combine. Set aside
Whip the meringue:
Beat the egg whites on medium speed until frothy, add vinegar and whip until it turns whitish and air bubbles are fine. Gradually add the sugar as you beat, in 3 batches. I beat them at medium speed (speed 6 on Kitchen Aid). This will take a bit longer compared to beating at high speed. I used to do higher speed (speed 8), but the meringue is smoother, more stable and nicer when I maintain the speed on 6. I highly recommend stopping several times to check on the consistency and scraping the sides of the bowl to make sure no sugar left on the side of the bowl. Whip until you reach a stiff peak but still have a slight bent on the tip. Then lower the speed to 4 and whip for 1 minute to even out large bubbles and stop beating
If you beat until the meringue clumps on the whisk attachment in one HUGE chunk/lump, you know you've gone too far beating the meringue. You will have to start over when you overbeat the meringue. If you use it, the meringue will separate when you fold it into the yolk batter and won't hold much air and your cake will deflate later
Fold meringue into the cake batter:
Gently fold 1/3 of the meringue into the thick batter. Using a whisk, using a cutting motion and fold over to mix. Repeat this motion several rounds. Continue on with the second 1/3 of the meringue again to mix. For the last 1/3 of the meringue, use a rubber spatula instead to ensure you get all the batter at the bottom of the bowl mixed in as well. Use a cut down in the middle and fold over motion to fold gently but quickly. Make sure you don't see any more white meringue. Add the lotus Biscoff bits you crush earlier and fold gently to combine. The mixture should be fluffy and voluminous.
Pour the batter into an UNGREASED chiffon cake pan. Use a rubber spatula to smooth the surface. Gently drop the cake pan from about 10 cm height on the counter 2-3 times. Use a skewer to draw a zig zag to pop bubbles inside the cake batter.
Baking:
Pop into the oven and let it bake at 330 F for 50-55 minutes or until a cake tester comes out clean
You can also touch the top and if it springs back, it's a good sign that it's cooked through. I like to have some golden brown on top. Don't be alarm if your cake has some cracks on top. What you are looking at will become the bottom of your cake. I know many people mind it a lot and make a big fuss when the top of the chiffon cake cracks, but actually it's not a flaw.
Invert to cool down immediately:
Once out of the oven, drop the cake pan from about 10 cm height on the counter several times to prevent shrinkage. Then carefully invert the pan upside down immediately. Your chiffon pan may have the little stands for you to invert. Please don't be tempted to remove from the pan if it's still warm. It takes about one to two hours to cool down completely
Once it's cool down completely, use a spatula knife to run through the edge and the outer center of the tube to help release the cake. Gently push the base to lift the cake out. Use the knife again to run through the base of the pan and then carefully release the cake
How to store:
Once the cake has cooled down completely. Store in air-tight container at room temperature for about 3 days