Chocolate – Does vanilla powder really prevent melted chocolate from seizing

I don't know the details of this particular recipe, so you'll have to excuse me if this comes across as a bit of a shot in the dark, but here are a few things that could have gone wrong:

• Grainy chocolate is usually a sign of seizing. White chocolate still contains cocoa butter and can still seize. Therefore it's important not to let any liquid touch the melting chocolate and to not let the temperature get too high.

• 130-140° F is definitely way too high. White chocolate will normally burn or seize at temperatures higher than around 110° F. You mentioned that the second time you used the right temperature, but it's worth pointing out anyway: Be very careful with the temperature, don't use direct heat preferably, use a double boiler or a stainless steel bowl placed over a steaming pot, and stir frequently to keep the temperature even.

• Don't dump hot cream into the chocolate. It's strange that almost every recipe tells you to do this; water causes melted chocolate to seize, period. The only way to avoid this is to use a very large amount of liquid for a very small amount of chocolate, so what you have to do is go the other way; incorporate the chocolate into the cream, a small amount at a time. This is especially important with tempered chocolate because you've essentially raised the melting point!

• Also be careful not to let any water get into the chocolate as it's melting; use dry utensils and make sure you don't have any steam condensing over top (use a large bowl over a small pot if you don't have a double boiler).

• Finally, as Joe commented, make sure you're using the right kind of white chocolate. I've never seen baker's white chocolate, so when I need white chocolate for melting I generally use the white chocolate chips. If yours didn't burn at temperatures as high as 130° F then you might have been using coating chocolate instead.

Follow all those precautions and you should end up with a very smooth mixture. I've done this for ganaches and even foams and it's never a problem if you're careful about both the temperature and moisture.

From the recipe and your "fudge" description, I think the problem was that you didn't get enough air in the batter. Trying a different recipe is a good idea.

The way to get more air into a flourless cake is through the eggs. Look for recipes which require you to beat the egg whites separately to soft peaks. Mix everything very carefully, in the correct order. If your try still doesn't get you enough air, try more tricks. Whip your yolks with some liquid (maybe 10 ml per yolk) over a water bath (keep it between 60° and 70°C!), practically creating zabaglione. But really watch the temp with a probe thermometer - you don't get a good emulsion below 60°C, and you don't want your proteins to coagulate while whipping, they must do it latter in the oven (they start a bit above 70°C).

The other problem is that you might get too smooth a texture. First, select a recipe with less fat. Fat makes the batter softer, but also very smooth. Your hunch is correct: Choose a recipe which calls for both cocoa powder and chocolate. The powder has much less fat, resulting in a higher percentage of starch, and that creates a more cakelike texture. Another good way to change the texture is to use recipe which includes a nut flour. A raw almond flour will give you very little change in flavor, but if you don't mind deviating from the original, roasted hazelnut pairs very well with both chocolate and raspberry.

And as we are speaking of fat: you must use a good chocolate! Standard chocolate bars (Hershey, Milka) are no good. To cut costs, they use vegetable fat instead of cocoa butter, which changes the texture a lot. Then there are the manufacturers who use emusifiers and include even less cocoa butter. If you can get hold of real confectioner's chocolate (Valrhona, Callebaut), use it. If not, buy a chocolate bar which contains only cocoa mass, cocoa butter and sugar and nothing else - no vegetable fat, no emusifiers, etc. Also no milk solids, you want to make this kind of recipe with bittersweet to bitter chocolate. The one big brand I use for baking is Lindt Excellence (not Lindt Lindor!), but there are also some supermarket-branded chocolates with the right contents.

I don't have a tried recipe to offer you, but I am sure that the usual suspects have published something good. I think Smitten Kitchen had a nice big post on flourless pastries ones (but don't remember if they had a choco cake there), and Lebovitz and/or Desaulniers probably have recipes for a flourless choco cake too.