The traditional mould for baking Castella cake is a bottomless wooden
Where to get a Castella wooden mould? You could buy one, make one, or improvise with my method. I put the pan holding the batter in a bigger pan, and there's corrugated cardboard tucked in the space between the two pans. To prevent the cardboard from catching fire in the oven and then burning down the house, I wrap it in foil.
Once you get the mould sorted, you need to pick a recipe. Which one should you go for? Mine, of course!
My Castella cake is soft and moist freshly baked. Yup, you don't have to wrap it in plastic and wait a day before eating it. Nope, I don't cheat by adding oil or that awful stuff, ovalette (aka SP). Neither do I sneak plain or cake flour into the cake. I use only only bread flour, as I'm supposed to, but the cake eats like it's made with cake flour.
How do I make a stellar Castella cake?
I start by beating 85 g egg whites with 60 g sugar till firm peak stage, i.e. between soft and stiff. Too much egg white would make the top of the cake wrinkled after cooling down. Too little would result in a dense crumb. Underwhisking would result in the cake collapsing. Whisking too quickly or too much would make the crumb coarse and holey.
Once the meringue is firm yet smooth and creamy, I add 60 g egg yolks. Most home recipes use an equal number of whites and yolks but I use more yolks than whites. Why? To help make the cake soft and moist, and the top flat and wrinkle-free. The yolks must be added one at a time or the meringue would deflate. And the whisking must be done at low speed, to help remove big air bubbles in the meringue.
There is, of course, honey in honey Castella cake. How much? Just 20 g, enough to flavour the cake but not make it sticky. Honey is whisked into the batter after the egg yolks.
After the honey comes 60 g bread flour. The less flour there is, the softer the cake is. Unfortunately, too little flour would result in a coarse crumb and a crumpled top, two definite no-no's for Castella cake. Too much flour would make the cake dense and hard, another hallmark of Castella cake failure. Getting a tight yet soft crumb requires great balance.
The last thing added to the batter is 20 g milk. As I fold it into the other ingredients, I bang the mixing bowl against the worktop from time to time to help remove big air bubbles.
Halfway through the mixing, I let the batter rest for a few moments. Perhaps thinking the coast is clear, some unsuspecting air bubbles rise to the surface. And that's when I nap 'em. Bang! Bang! I'm so sneaky, yah?
Transferring the batter into the cake pan gives me another chance to catch those nasty bubbles. I pour slowly, from a height, so that some of the big bubbles burst as they flow out of the bowl. What do I do before the pan goes in the oven? Yup, bang bang! It's zero tolerance for Castella cake's #1 enemy.
Which shelf in the oven do I use? Bottom, so that the bottom of the cake browns as nicely as the top.
After the cake is done baking, I drop the pan from a height to stop it from shrinking excessively as it cools down. This is the neatest trick I've ever come across in cake making!
Here's another good trick: invert the pan and let it rest on a wood chopping board for a few moments. This helps keep the top of the cake flat and smooth.
Just before serving, trim the edges of the cake. The cuts must be neat and clean or you've failed even if the cake is perfect in every other way. I hope you're the obsessive-compulsive type?