INGREDIENTS:
1 cup sugar
Finely grated zest of 3 lemons
4 large eggs
3/4 cup freshly squeezed lemon juice (from 4 to 5 lemons)
2 sticks plus 5 tablespoons (10-1/2 ounces) unsalted butter, at room temperature and cut into tablespoon-sized pieces
1 fully-baked 9-inch tart shell
DIRECTIONS :
1. Have an instant-read thermometer, a strainer and a blender (first choice) or food processor at hand. Bring a few inches of water to a simmer in a saucepan.
2. Put the sugar and zest in a large heatproof bowl that can be set over the pan of simmering water. Off heat, rub the sugar and zest together between your fingers until the sugar is moist, grainy and very aromatic. Whisk in the eggs, followed by the lemon juice.
3. Set the bowl over the pan, and start stirring with the whisk as soon as the mixture feels tepid to the touch. You want to cook the cream until it reaches 180 degrees F. As you whisk -- and you must whisk constantly to keep the eggs from scrambling -- you’ll see that the cream will start out light and foamy, then the bubbles will get bigger, and then, as the cream is getting closer to 180 degrees F, it will start to thicken and the whisk will leave tracks. Heads up at this point -- the tracks mean the cream is almost ready. Don’t stop whisking and don’t stop checking the temperature. And have patience -- depending on how much water you’ve got under the cream and how much heat you’re giving the cream, getting to temp can take as long as 10 minutes.
4. As soon as it reaches 180 degrees F, remove the cream from the heat and strain it into the container of a blender (or food processor); discard the zest. Let the cream rest at room temperature, stirring occasionally, until it cools to 140 degrees F, about 10 minutes.
5. Turn the blender to high (or turn on the food processor) and, with the machine going, add about 5 pieces of butter at a time. Scrape down the sides of the container as needed while you’re incorporating the butter. Once the butter is in, keep the machine going -- to get the perfect light, airy texture of lemon-cream dreams, you must continue to beat the cream for another 3 minutes. If your machine protests and gets a bit too hot, work in 1-minute intervals, giving the machine a little rest between beats.
6. Pour the cream into a container, press a piece of plastic wrap against the surface to create an airtight seal and chill the cream for at least 4 hours or overnight. When you are ready to construct the tart, just whisk the cream to loosen it and spoon it into the tart shell.
Serving:The tart should be served cold, because it is a particular pleasure to have the cold cream melt in your mouth. Fruit coulis is nice with the tart, but not necessary, ditto a little crème fraiche. I know it sounds odd to offer something as rich as crème fraiche with something as rich as this tart, but it works -- because the lemon cream is so light and so intensely citric, it doesn’t taste or feel rich, a situation that is potentially dangerous and positively delightful.
Storing:While you can make the lemon cream ahead (it will keep in the frige for 4 days and in the freezer for up to 2 months), once the tart is constructed, it’s best to eat it the day it is made.
