Okay, let me try to elaborate with photos and some description. Please note that my wording might not be precise enough.
For most of the desserts that need Meringue for being the structural support, it's always critical to keep as many air bubbles as possible. I guess, that's why we were always told to "keep the container for Meringue free from egg yolk/oil".
So for me, below preparations can maintain as more bubbles as possible:
1. Ensure everything is 'Mise on place (putting in place)' - ingredients, tools, and a pre-heated oven. For the ingredients, they need to be weighted, sieved (powder like flour, corn starch, powder sugar, cacao powder, etc); for tools, they need to be gathered and arranged (like the parchment paper in the baking tray).
The better the preparation is, the quicker the finished batter can be sent into the pre-heated oven - this will save a lot of bubbles.
2. Generally, you will need to prepare Meringue - egg white, sugar, lemon juice (not 100% necessary for me). Meringue is a tricky thing itself and needs practices. From the practices we observe and learn what is the right status we need for different desserts. When it's not fully beaten, it can't support the structure properly; when it's over-beaten, it might cause the deformation and cracks. For chiffon cake, I usually beat the egg white until such status.
3. Generally, you need to prepare (A) egg yolk + vegetable oil + milk + flour and (B) Meringue. I will always prepare (A) first, as nothing can go wrong (flour has to be sieved, don't heat up milk too much). 80% of the "Mix it enough to be a proper cake" should be done here.
After (A) is done, you can start prepare (B), because (B) needs more attention. Also, you don't want to prepare (B) first and let it sit and wait for (A) - air bubbles will disappear, too.
(B) usually won't take too long - 1 minutes low speed until large bubbles appear --> add 1/3 sugar and turn to high speed --> for another 1/3 sugar --> the rest 1/3 sugar
Now you have (A) and (B), your baking tray is ready, and the oven is also pre-heated to the needed temperature.
Let's start mixing. As we mentioned in the beginning, the bubbles in the Meringue don't like oil. Compared with the very light Meringue, (A) is very oily and sticky. If you dump (A) directly into Meringue --
- air bubbles will disappear in a terribly quick speed
- it's more difficult to properly mix them
4. So, an extra "tempering" step will help - get 1/3 Meringue into (A) and mix them properly. This 1/3 Meringue will loss more air bubbles, but meanwhile, it can make the texture of (A) much lighter and easier to mix with the rest of Meringue.
5. After the 1/3 Meringue is well mixed with (A), you can now put (A) into the rest of Meringue. Now, it's the last 20% of "Mix it enough to be a proper cake" - the key is to ensure the bottom part has to be thoroughly mixed, too.
As we already do a lot of efforts to keep as more air bubble as we can, you don't need to worry too much in this step. Usually, the final mixing should be properly done within 1 minute.
(Upper photo: after 1/3 Meringue is mixed with (A) / Lower photo: after (A) is mixed with the rest of Meringue)
6. The batter is done and ready to be filled into the baking tray. You can use a little oil on the tray to "fix" the parchment paper. Ideally, the batter should be thick enough but still able to naturally flow (not runny) to the corners when you slightly shake the tray. If it's not that easy to flow, you can use a spatula or a dough cutter to adjust and flatten the batter. Then, just send the tray to the pre-heated oven.
7. The baked cake has to be cooled down soon. You can hold the parchment paper and let the cake sit on a cooling rack. As you see, my cake cracks a bit, too. I am experimenting how much greentea powder I can add into my batter. It doesn't have to be perfect. Here you can also see that my cake is pretty thin, might be just half inch. The thickness will affect the baking time and temperature, and this is something you will need some experiments.
8. The cake won't take long to cool down, and 10 minutes should be sufficient. Now, you will need to cover the cake with another parchment paper or silicon baking matt, turn the cake upside down, and peel the parchment paper underneath the cake. If the cake is well bake, you should be able to peel the paper and get a very clean, towel like surface.
9. Then, put the peeled parchment paper back, and turn the cake back. You can slight cut on the end you will start rolling - it helps.
10. After adding the filling you want, it's time to roll the cake. When you use a larger piece of parchment paper, you can grab both ends and force the cake to roll. The above pre-cuts will give you a good start.
Keep using the two ends of parchment paper to roll.
Ensure the edge is at the bottom.
