so the last couple of genoise that i a made all had the same problem: they all rose to the top of the pan and by the end of the process, the edges were still tall but the rest of the cake sank. i followed rose’s recipe, warmed the eggs and sugar mixture, mixed on full speed on the KA mixer for the full 5 min and folded the flour with the balloon whisk ( even got the matfer whisk). I was so happy to see that i hardly lost any volume after getting that giant whisk!!! but the cakes still sank towards the end of baking in the oven and i end up with cakes that i can’t even slice because the middle is so thin compared to the tall sides.  What am i doing wrong???

What is the temp of the egg and sugar mixture after you warm it? The temp shoud be about 85 to 90(not about 100). Do you have the oven temp, and do you use the super-fine sugar?

Is your oven hot enough, and are you baking long enough?  Are the sides of the cake pulling away from the pan, and the top flattening slightly before you take it out of the oven?  Are you unmolding immediately and cooling with the top crust up?

Falling in the middle can be a sign of underbaking.  With an instant read thermometer, the cake should register above 190F when you pull it out, and the sides/top should shrink back slightly.

A few other things to check:
-are you weighing eggs, flour sugar and cornstarch?
-are your yolks particularly small?

I had the very same problem ever since moving into our new home. I was VERY frustrated after years of never having a problem with this cake. I made 4 cakes in a row to try to figure out what was wrong. Each of them did the same even though I checked and double checked everything.  Haven’t figured it out yet so I’ll be following this post to see what other suggestions are made.  In my case, I’m beginning to suspect the problem is with the top oven element not giving me even heat and am having that looked into.

R u opening the oven door to check things prior the baking time indicated on the recipe?  And and said, let us know what is your oven temperature checked with a thermometer.

No I put the oven thermometer in the oven beforehand and left it in the entire baking time. I got the correct temperature but I think the heat is coming mainly from the bottom element. For example the last cake I made I had to turn the broiler on to brown the top of the cake because it was well beyond the baking time required and still not browning or even golden on the top.
I’m finding my search for a good oven rather confusing. I know that price is not always a good indicator of better quality.  I have a friend that has a very expensive brand and has had nothing but trouble, having had to repair the oven 4 times in the last 3 years. The best oven I ever had for baking was a cheap department store brand. Unfortunately it was a wall oven and had to stay in the house when we sold it.  I don’t have any choice now except to use the convection feature on mine when baking but I don’t like it because the cake has a tendency to get very dark or even burn where it is closest to the fan so I have to turn it part way through to prevent that. It’s too bad you can’t test the oven in the store ...wouldn’t that be fun….

I never had a problem regarding bottom heat vs tops not browned.  We mostly bake with bottom heat ovens!  Heat rises, so if you position your oven rack higher it will brown faster.  Cakes recommend to be on the middle of the oven (instructions says to place the oven rack in the lower third of the oven but this actually means that when u place ur cake, the cake itself is in the middle or just around there.

The oven needs to preheat for a minimum of 30 minutes.  DO NOT rely on the preheat function of your oven.  My oven says it is preheated just in 10 minutes but this only means the built in oven thermometer detects the dialed temperature.  Most all built in oven thermometers are on the ceiling of the oven!  I place my Thermoworks or CDN oven dial thermometer on the rack of the baking cake and it takes 30 minutes!

Again, did u open the oven door prior the recipe baking time?  This is the main reason foam cakes such as genoise collapse.

Also, you may want to check if your oven dial thermometer is accurate!

Regarding heating eggs, it won’t cause the collapse.  85-90 oF is fine, I heat mine to 110 actually.  Be sure eggs don’t scramble!

Oh, do note, the oven dial thermometer will go down in temperature when u place ur cake.  This is expected.