Genoise is the classic French sponge cake. Its exhaustive list of ingredients includes eggs, sugar and flour. And maybe a wee bit of butter. But that’s it.
Just think for a minute about how amazing that is. Eggs are individually packaged vehicles containing fat and protein. Sugar is a crystalline sweetener that gives nice caramel flavours when it’s heated. Flour is a powdery form of wheat, and provides structural support for most things in the pastry kitchen. Butter is, well, fat.
Under the right circumstances, these ingredients come together to form a complex network of teeny tiny air bubbles.
First, heat eggs and sugar to 45 degrees Celsius, then whisk until cool. This magical temperature is just hot enough to loosen up the proteins in the eggs, but not so hot that you end up with sweet scrambled eggs. With vigorous whisking, this dense, yellow liquid is magically transformed into a pale yellow foam that is twice, sometimes thrice, its original volume. It doesn’t matter how many times I make genoise – the beauty of the foam shocks me every time.
Gently, oh so gently, fold in the flour. This terrifying step is dreaded by most culinary students, since it’s a fine balance of incorporating the flour just so without deflating your egg foam. After a bit of practice, you learn to read the batter. It whispers to you when it’s done – you just have to keep your eyes and ears open.
If you’re daring, you’ll fold room temperature (not hot, not cold), melted butter into the mix.
But that’s not all. Now you have to gently coax the batter into a prepared pan, and slide it into the oven. All those old-fashioned stories of moms shooing their bouncing kids out of the kitchen when a sponge cake was in the oven? I get it now. Nothing comes between me and my genoise.
After all that, if you’ve done your job properly, it comes out of the oven golden-brown, moist and fragrant. That’s alchemy, if I ever saw it.