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I've been baking this recipe for over a year now, flavour and texture are wonderful, the guests love it but half of the time I get these air pockets on the bottom of the cake.

The air pockets appear at the center of the bottom and also at the sides. Sometimes they're barely there, sometimes they're big enough that I'm unsure if i'll serve it to guests (for exemple when they're 3cm height).

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Recipe is as follows:

  • 150g cashew nuts (roasted, unsalted) chopped in a food processor
  • 30g white flour
  • 125g sugar
  • pinch of salt
  • 4 egg whites, lightly beaten with a fork
  • 150g butter, heated untill brown
  • 1/2 teaspoon vanilla extract

Everything at room temperature.

Preparation is staightfoward: mix dry ingredients, add egg whites, add butter and vanilla. Cooks at 160~180C for 45~50m untill golden brown. Lower temperatures do not make the bubbles disappear.

What causes these air pockets? Has anyone faced a similar issue before?

rumtscho
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maya
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  • How thick is the batter? If it’s pourable, this would be surprising. (I usually bang the cake pan a couple of times in case there are bubbles, but this won’t help if the batter is so thick it needs to be spread) – Joe Nov 26 '20 at 14:55
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    Pretty pourable! No need to spread. I also bang the cake pan before going to the oven. – maya Nov 26 '20 at 15:08
  • Does this answer your question? [How to avoid holes in Chiffon cake?](https://cooking.stackexchange.com/questions/102601/how-to-avoid-holes-in-chiffon-cake) – GdD Nov 26 '20 at 15:10
  • I had the same problem with my chiffon cake @maya, and asked the same question. The answer solved the issue. – GdD Nov 26 '20 at 15:11
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    @GdD The thing is that the holes aren't inside the cake. When i cut a slice, it's perfectly smooth in texture. The bubble is forming only on the bottom, on the outside of the cake. Despite that, I already tried to run the knife and also to bang the cake pan - to no effect, sadly... – maya Nov 26 '20 at 15:29
  • Did you use parchment paper or similar in the bottom of the pan? – Debbie M. Nov 26 '20 at 22:20
  • I didn't get that @maya, in that case this isn't a dupe. Is there a hot spot on the baking pan? – GdD Nov 27 '20 at 08:09
  • @DebbieM. No parchment, just butter and flour on an aluminium 18cm pan. – maya Nov 27 '20 at 14:56
  • @GdD English isn't my native language, not sure I understand what you mean by "dupe". What you see at the pictures is the flipped cake, that air bubble is forming at the bottom. I tried different temperatures, running a knife through the batter, lining the pan with antiadherent plastic, baking at the gas oven, baking at an eletric oven, the bubble keeps showing up and I can't for the life of me figure out what's causing it ): – maya Nov 27 '20 at 14:59
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    @maya, dupe is short for duplicate, apologies for confusing you. I am wondering if the same thing happens in a different pan. It could be part of the bottom of the pan has some sort of imperfection which transfers heat differently from the rest. The cake looks very nice anyway, makes me want a slice! – GdD Nov 27 '20 at 15:36
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    @GdD Oh I get it now! Well, I bake that cake often, sometimes twice a week. I have 3 pans, same size and material, but purchased along the years... I had my suspicions about a heat spot, but the many pans and 2 ovens do make that unlikely. The weirdest part is that half of the time the cake will turn out perfectly smooth on the bottom, out of the blue – maya Nov 27 '20 at 15:51
  • As it’s a pourable batter, do you pour it in a ring, or just pour in the middle and let it spread? My only other idea is if it’s somehow cooking from the outside edge in and causing some sort of buckling that pushes up the middle, but I would think there would be a bit of a vacuum to hold it down unless there was air trapped down there. But if this is the case, you might try the recommendations at https://cooking.stackexchange.com/q/13167/67 – Joe Nov 27 '20 at 17:31
  • @Joe I pour it in the middle and let it spread (it does, quickly). The idea of buckling makes sense, but would it cause the bubbles at the edges also? You can notice at the right side of the right image that the bubbles are also forming at the corners. The link is very good, i'll look at it carefully. Thanks! – maya Nov 27 '20 at 22:05
  • @maya : the 'buckling' idea is basically that if the batter expands slightly when forming a crust, and it cooks faster at the edges, there's no space for it to expand when it gets to the middle, and so it bows up. I don't think it would explain large bubbles around the edges. (I had assumed the picture was showing something like problems getting it to release from the pan) – Joe Nov 28 '20 at 17:13
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    @Joe The pictures show the air pocket that forms at the center and also the small pockets at the edges. After 10m at room temp if comes out of the pan with no struggle. The bubbles are underneath the cake, so only when unmolded can I see if I got them or not. I'm planning to bake one at a pyrex dish and watch it cooking so I can hopefully see when and how they form. – maya Nov 28 '20 at 18:49

1 Answers1

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That happened to me as well. Luckily it doesn't change the taste, but it is annoying! It comes from air pockets which formed because you whisked/mixed your cake batter too intensely, and/or for too long, which creates air bubbles. So first, it is best to mix your ingredients delicately, try to avoid incorporating too much air (easier said than done), and stop whisking once your batter reached the desired homogeneous consistency (overwhisking is a common mistake). Then, when you pour your cake batter in the pan, it's better to avoid pouring it all at once in the center, it will also create air bubbles. It's better to pour it delicately from one corner and let it spread by itself in the dish. Finally, before putting in the oven, tap (delicately) the bottom of your pan on the counter to free the remaining air bubbles and let them reach the surface before cooking. I hope that will help, let me know!

Sarah BDnO
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  • At first I also thought I was overmixing. I reduced the mixing steps to 20 or 30s, just untill the ingredients are combined. But bubbles kept coming from time to time. I always poured the batter at the center, I can't see how that would create bubble, but I always tap it before baking. I will try pouring from a corner! From the date of my entry I've experimented with this recipe, baked 42 of them taking notes. No clear answers still. But I discovered this is a kind of "financier", a french cake. – maya Jan 05 '21 at 21:51
  • Interesting, and very mysterious! Does it happen only with this specific recipe or with others as well? Have you tried baking it in smaller quantities? Normally financier is baked in a small pan, so maybe the batter doesn't react the same way in a bigger one? – Sarah BDnO Jan 06 '21 at 09:59
  • The bubbles appear even in small cupcake format. But I like to make mine as a whole cake, following the recipe. The bubble persists with all nuts: pistachio, cashew nuts, almonds... My guess is that water from egg whites is the main leavener agent. Steam must be forming in big quantities at the start of heating, creating those big bubbles. – maya Jan 10 '21 at 23:05