The Stirring Mistake That Causes Oily Ganache
Making ganache is one of the richest things you can do with chocolate. A combination of heavy cream and melted chocolate, ganache serves as a base for multiple desserts such as chocolate truffles, lava cake, hot fudge, and deliciously pillowy namelaka. Here's the thing about ganache, though. It can go from smooth and glossy to split and oily in a flash. And while there are several ways this can happen, one of the easiest mistakes to make is to over-stir your ganache.
As ganache is, at its core, a mixture of ingredients that don't naturally bind together, a fair amount of stirring is required in order to bring it together. However, once you've gotten the ganache to that point, stop stirring immediately. Suppose you continue to stir past the point where the ganache has become fully emulsified. In that case, you will actually end up separating the oils and fats in the chocolate, resulting in a seized, grainy ganache.
Stopping once the ganache is mixed smoothly allows it to begin its natural process of setting. Ganache hardens as it cools. By ceasing stirring, it cools as a cohesive whole without separating. Still, you wonder, if I have over-stirred my ganache and it's gone grainy, is there any way to fix it? Of course, there is.
How to fix over stirred ganache
Here's a bit of irony for you. To fix a ganache that's been split by over-stirring, you actually need to stir it a bit more. The trick is to mix in additional liquid so that the chocolate fats have something to emulsify with. Unfortunately, by adding more liquid, you do end up diluting the ganache to a certain degree. This means that you won't achieve the kind of firmness required for making chocolate truffles. Still, a smooth, diluted ganache works for hot fudge, and as a glaze for cakes.
The dilution amount depends on the type of liquid you use. For instance, adding boiling water and gently reheating the ganache over a double boiler will yield a much runnier ganache. The same is true of using milk or cream, but the ganache will be a little richer thanks to the milk proteins. You could use some kind of viscous sugar, like corn syrup or honey. Slowly heat and whisk the sugar in until it reforms the ganache into the smooth consistency you desire.
Adding more chocolate is also an option. This is best for saving truffle ganache because the extra chocolate results in a richer, stiffer ganache. Whatever route you take, keep faith in knowing that not all is lost just because you over-mixed your ganache. You can still save it and have it be as rich and flavorful as ever.