I've already talked to you about the rather special case of
warm emulsified sauces (béarnaise, hollandaise) and how to make up for them in the event of tragedy, so I won't go into that again, but this time we'll concentrate a little on creams.
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.