Tranchée?
When a cream "tranche", a french chef word, it's simply no longer homogeneous: instead of a single part, there are several parts in the bowl or saucepan, of different textures, liquid and solid in general.That's just what "tranchée" means: the taste is unaffected, but the texture is completely, and we amateurs simply say "missed", "failed", "screwed up" or many other terms...
What's happened?
It's difficult to make a general rule but it can be summed up as "There was too much..." or sometimes "There wasn't enough...".Too much can be an ingredient, a duration, a temperature.
Too much of what? Well, that's where it becomes very much a question of the preparation you were doing, so let's look at a few emblematic cases.
The custard
the custard you started with suddenly turns into a big lumpy mess, you've probably overcooked it by more than 185°F (85°C), or cooked it too quickly (over a hot fire).To make up for this, try giving it a good whirl with the mixer.
A ganache
A ganache that tranche is very often a temperature problem: the chocolate begins to set on its own, resulting in lumps, because the temperature of the mixture is heterogeneous.To make up for this, try putting it in the microwave for a few seconds, before whisking or even mixing vigorously, to bring the mixture back to an even temperature.
A mixture of cream + an acidic ingredient
If you add lemon juice directly to crème fraiche (for example), there's a great risk that it will curdle, which is normal, and therefore slice. To avoid this, you can 1) use liquid cream, for which there is less risk 2) add a pinch of bicarbonate of soda to the lemon juice, which will foam up a little but is harmless.Note that in this case, cream that curdles is unfortunately irrecoverable: your cream has turned into cheese.
To sum up: although cream curdling can be very stressful during preparation, it's not always irreversible, and can often be remedied by a simple gesture.
