The Most Extraordinary Lemon Tart Re-thunk
Well, I made the recipe over the weekend and I’ve got a new thought on how to speed up the process and still get the thick, smooth, almost velvety cream that makes this tart so remarkable.
To recap, the recipe calls for the sugar, lemon zest, lemon juice and eggs to be mixed together in a bowl. The bowl is put over a saucepan with a few inches of boiling water and you whisk, whisk, whisk until the mixture thickens enough for the whisk to leave tracks, then you keep whisking until the cream measures 180 degrees F on a candy or instant-read thermometer. To finish the cream, you pour it into a blender and cool it slightly before you whir in room-temperature butter — but that’s not the problemmatic part.
So here’s what I did over the weekend — I got bold! To make my double boiler, I used a soup pot and I filled it about 2/3 full of water, which I brought to a boil. I then put the bowl (a metal bowl) with all the ingredients over the steaming soup pot (making sure that the bottom of the bowl wasn’t touching the boiling water) and whisked like mad. With so much heat under the bowl, the cream came up to 180 degrees F in under 10 minutes (in fact, the first time I did it, it took 4 minutes and 39 seconds; the second time, it took almost 7 minutes — different bowl, different pot, different stove).
Of course, if you’re going to supercharge the power under the bowl, you’ve got to be vigilant — you can’t take your eyes off the cream; energetic — you can’t stop whisking, even for a few seconds; and nimble — as soon as the cream shows the slightest signs of thickening, measure the temperature and make sure to remove the bowl from the heat immediately the instant you hit 180 degrees F.
A couple of other re-thinks: If your lemon zest was very finely grated (I use a Microplane grater/zester), then you don’t need to strain the cream — just quickly scrape the hot cream from the bowl into the blender. And, while you shouldn’t add the butter to the cream while it’s still very hot (if you do, then the butter will melt, as it does in a lemon curd, and you won’t get the great texture that sets this cream apart), you don’t really need to measure the cream’s temperature before you butterize it — if you leave the cream in the blender for 8 to 10 minutes, it will be just the right temperature for blending in the butter.
Finally, I made this tart on Sunday as part of my workshop at Pastry Scoop’s Spring Conference at The French Culinary Institute, and, because it was at hand, I used lime juice in place of the lemon juice and it worked perfectly.
I hope those of you who haven’t already made the tart, will — it’s really one of my all-time favorite recipes — and that those of you who’ve already made it, will find these tweaks helpful the next time you decide to whisk up this treat.