Cooking custard sous vide
It’s an established fact that new owners of temperature-controlled water baths will quickly develop an urge to use them to cook everything in their kitchen. Sure, we all intend them primarily for meat and fish, but before long we start looking for ways to make mashed potatoes, or lentils, or… custard.
Ultimately, cooking custard sous vide is just a logical extension of cooking eggs with an immersion circulator. The same principles apply: cooking it for time-at-temperature to denature all the right proteins to thicken the custard, while preventing the eggs from curdling or developing “eggy” flavours. The traditional method for crème anglaise is to heat the dairy component, temper it into the eggs, then cook the whole base just until it reaches nappé consistency. If you overshoot and curdle the eggs, well, you can always strain it or blitz it with an immersion blender. But it’s never really the same.
As a trial run, I decided to make a cinnamon ice cream base, which is essentially the same thing as crème anglaise. I warmed some milk, cream, sugar, salt and cinnamon sticks, let it steep for an hour, then strained out the cinnamon sticks and mixed in the egg yolks, blending thoroughly. I chilled this base, then put it in a Foodsaver bag. This is the most difficult part of the process, since edge-style vacuum sealers can have a hard time with liquids. I just used the “pulse” button until the custard started to get sucked up toward the open edge, then manually sealed it.
The bag went into the water bath at 82°C for an hour. When it emerged, it was a perfect nappé consistency, with no curdled bits of egg and no eggy off-flavours. (I strained it just to be sure.) I chilled the base down, then let it mature in the fridge overnight, having read in the Fat Duck Cookbook that this step is important for crystallizing the milk fat, which is important for good ice cream structure. Anecdotally, I’ve never been as pleased with ice creams that I’ve chilled in an ice bath and churned right away as I have with those I’ve refrigerated overnight before churning.
The resulting ice cream was, in fact, one of the smoothest I’ve ever made at home, so I would definitely declare the process a success. Next time, though, I would probably just blitz all the ingredients together, put them in the bag with the cinnamon sticks (or other flavouring ingredients) and let them infuse the custard as it cooked, just to cut a step out of the process. I admit, though, that this is an area where I’m not sure whether sous vide takes some of the soul out of the process. I still feel it’s an important skill to be able to cook a custard on the stovetop, to get a feel for when it’s done without overcooking it. But the controllability of cooking it sous vide can’t be beat.