Making a genoise gluten free, recipe

I'm determined to never accept that a given recipe can't be made gluten free and delicious without at least attempting it.  Frequently, my attempts have more and more often presented "Different, but good" results.  This is one of them.

Genoise is a sponge cake that uses no chemical leavening and instead relies on air suspended in the batter during mixing.  You can imagine that gluten is very useful in such a cake.  At it's heart, the way the structure of baked goods is this: starch and protein work together to create a superstructure that at a microscopic level looks like bubbles of varying sizes stuck together.   Baking is basically the art of creating those bubbles, filling them with air, and then solidifying them so the structure remains even if the pressure that made the bubbles is released.  Think about the difference in a hot air balloon and a zeppelin. Gluten is a particularly good protein for making this structure because it's complex and wheat flour seems to have the perfect ratio of gluten to starch to make the textures we're used to. With yeast or baking soda or baking powder the bubbles that create air pockets are being created as it cooks (which is the process by which the stuff gets hardened).  With a genoise, all the bubbles you're going to get are put in during the mixing.  So through out the whole process,  it's really important not to collapse your batter, whether your flour has gluten in it or not.

Genoise is the cake ladyfingers are made from and thus a good base for tiramisu.  I haven't had tiramisu  since BC (before celiac) - that's my eventual goal.   I decided to attempt just the cake before attempting a full tiramisu - mascarpone is expensive and wasting it on a bad cake would be sad.

I started my efforts by speaking to a friend who has done a huge amount of cake bakery to ask about what flours to start with.  She recommended I start with teff flour.  I've never used teff flour before but I'd eaten things she'd made with teff and they were yummy, so I took her suggestion.

 I wasn't especially experienced in baking prior to going gluten free, so some of these difficulties could be due to my inexperience rather than the imperfections of the ingredients, so it's possible the recipe that will follow may be perfectly good as is.

This recipe was adapted from the America's Test Kitchen Baking Book and because it's pretty complex.


My recipe:

1/2 cup white rice flour
1/2 cup teff flour
1/4 cup tapioca starch
1/2 teaspoon xantham gum
1/2 teaspoon salt
 5 large eggs, room temperature (this is important)
1 teaspoon vanilla extract
5 tablespoons unsalted butter (do not use salted), melted and cooled (do not put hot butter in this batter)

1.  Adjust oven rack to middle position and preheat to 350 degrees. Line the bottom of a springform pan with parchment paper and don't grease.  Sift flours together with salt and xantham gum, making several passes through the sifter and whisking, until well mixed and as fluffy as you can make the flours.  Set aside.  If you melt the butter now, it should be properly cooled by the time we need it further on in the recipe.

2. In a large bowl, one small enough to fit across a saucepan but large enough to be suspended above the bottom of the pan, whisk the eggs and sugar together.  Get a saucepan of water just simmering and set bowl on top of it, making sure the water doesn't touch the bottom of the pan. Heat the egg mixture, whisking constantly, until it's warm but not hot (think bathtub warm) or an instant read thermometer says 100 degrees. (1-2 minutes, says the original recipe, but mine took longer.  The temp is more important than the time).

3. Remove from the heat and whip the mixture with an electric mixer on medium-high speed until very thick and voluminous - you want the batter to "ribbon"  - fall in thick ribbons that rest on the top of the batter.  4-6 minutes. Compare how much fuller the bowl is from the previous picture.  I probably could even have whipped it longer - the more whipped your eggs are the more denatured their proteins and the easier it is for them to form new bonds and get that structure you want.  Whip in the vanilla.

4.  Transfer 1 cup of mixture to a medium sized bowl and set aside.  Sift half of the flour mixture over the remaining egg mixture and fold very gently wiht a large rubber spatula, 12 to 15 folds.  The larger the spatula, the better.  You want to turn over the maximum amount of batter for the minimum amount of agitation.  Every stir pops bubbles and your batter is now as leavened as it's ever going to be.  Sift the remaining flour in, and fold in very gently 8-12 folds.

5.  Remember the butter and the reserved batter?  Gently mix them together and then fold that into your batter as well.  4-6 folds

6. Immediately scrape batter into prepared springform, being careful not to deflate the batter- hold the bowl as close to the springform pan as possible (you may want help), and do not scrape the excess batter from the spatula into the pan.  Don't jostle the pan and do not turn during baking. I placed the springform on a cool stove right above the oven so it moved a minimum amount after it was in the pan.  Bake the cake until it turns a deep golden brown and a toothpick comes out with just a few crumbs on it, about 22 minutes.

7. Let the cake cool completely.  If you want to turn it into a layer cake, I recommend freezing the cake in the springform pan and only removing it from the pan after it's frozen. Use a long knife to cut parallel to the bottom about half way up.  If you have a bread knife longer than the diameter of your cake that's perfect, but we made do with a shorter one, making small delicate cuts in radii around the cake.