After cranking out sad, flat genoise, one after another, I am extremely elated to announce today that I finally made a successful genoise—1.5 in. high at the center, 1.25 in. high at the edges, and almost no flour nuts! What’s more, I was able to do all of this without a scale, so yes, it is possible, just cumbersome and perhaps not so consistent.
Since I finally figured out what went wrong with all those failed genoise, I want to share what I learned from the experience. Essentially, most of the factors that can screw over your genoise happens before the cake gets in the oven. The only thing that can really go wrong once the batter is in the oven (assuming it was properly mixed) is wrong oven temperature or opening the oven door before the cake is done. If you are having trouble with the genoise classique, go through this checklist as you are making the cake.
The most crucial measurements are for the eggs, since they provide the structure. Weigh yolks and whites separately. The recipe calls for 4 large eggs (200 grams), so you need 120 g whites, 80 g yolks. (30 g/white, 20 g/yolk, 50 g/large egg) If you do not weigh yolks and white separately, you may not be getting enough yolks, which stabilize the egg foam. If you are using volume measurements, you need 3/4 c.+1/2 tsp. eggs (total volume) of which 1/4 c.+2 tsp. must be yolks.
Temperature is the important. If your eggs aren’t at the right temperature, you won’t have the right volume or stability. MEASURE the temperature of your eggs! Calibrate your thermometers in boiling water if they are not accurate. I have a thermometer that doesn’t go up to the boiling point of water, so I had to calibrate it with another thermometer, taking four data points (reading vs. actual temp.) and doing a linear regression on Excel.
In Shirley Corriher’s Bakewise, the recommendation is to heat the eggs no more than 90 deg F, so that the majority of the beating time will fall in the range of 75-80 deg, which is the optimal beating temperature for the eggs. Rose says to heat the eggs just to lukewarm or room temperature. Talking with some folks on this forum, Julie recommended 110-115 deg; Loopy (who lives in the Bay Area, like me) recommended 100 deg. I think I’ve always had the wrong egg temperature, and it has been frustrating that there isn’t a definitive number out there. Today, my kitchen in San Francisco was 62 degrees, and I tried Loopy’s 100 deg., which worked, so I took some data from this and used Newton’s Law of Cooling (http://en.wikipedia.org/wiki/Convective_heat_transfer) to develop a model for different room temperature and initial egg temperature scenarios.
The results of the model, and the photos of the cake, are here.
I will be happy to send you the Excel spreadsheet so you play around with it as well. Obviously, the model is only as accurate as my temperature measurements, and this model definitely needs testing. If anyone is making a genoise, please test some of my model’s predictions and report back!
To answer the question of what temperature you should heat your eggs to, you need to find an initial temperature to maximize the amount of time the eggs spend in the 75-80 deg range. If you work out the equation, Newton’s Law of Cooling shows that the time spent in the optimal range is independent of your initial egg temperature. HOWEVER, because the beating time is only 5 min, at moderate room temperatures (62, 70 deg), the eggs don’t have the opportunity to pass through the optimal range within 5 minutes if you use high initial temperatures (110-115), so it is best to use 90 degrees maximize the time spent in the optimal range. At lower room temperatures (40, 50 deg), the times are the same for all initial temperatures examined (90, 100, 110, 115 deg). The model shows that a 70 degree room temp and 90 degree initial egg temp. is the best combination (short of having a room temp at 75-80 degrees). (See the figures.)
If your kitchen temperature is 75-80 degrees, theoretically, you can just heat your eggs to room temperature and then beat. Your eggs would then spend a full 5 minutes in the optimal range. If your kitchen temperature is >80 deg, all you can do is heat your eggs to room temperature and beat. The eggs can never cool below 80 if your room temp is >80. Perhaps you can turn on the AC, if it’s worth it.
I’ve tried beating a genoise by hand, and it just doesn’t work well. (It takes 20 minutes, and it strains the wrists.) I’m not sure about a hand-held mixer, but the Newton’s cooling model will probably have to be adjusted for that situation. The model results given above are for 5-minutes at HIGHEST speed beating on a STAND mixer. If you have heated your eggs properly, the foam should fill 1/4 to 1/3 of the 5 qt. KitchenAid mixer bowl. That’s what I observed today, and it looks like Rose gets about the same volume if you look on her videos. You can check yourself at this point. If you don’t have the right volume, then you didn’t heat your eggs properly.
I can’t offer any advice on this, but today my stable egg foam didn’t deflate very much when folding the flour. So fight hard for a stable foam, and also get the Matfer whisk. My batter filled a 9x2 pan half way, which is reasonable. A 9x2 pan is 8 2/3 c. Eggs are 3/4 c, quadrupled to 3 c, then add 1.5 c of dry ingredients and sugar to get 4.5 c. total volume (very rough approximate, assuming no deflation), which is half of the pan.
I calibrated my oven once with an oven thermometer (calibrated in boiling water) and found that it was 2 degrees off at 350 degrees. Today, it was 9 degrees off! So check your oven with a calibrated thermometer EVERY TIME you bake a genoise. Don’t take any chances! If you notice that your genoise takes longer or less than 25 minutes to bake, then your oven temperature is wrong.