• 1 prebaked and cooled 9″ tart shell, like Easy Pat in Pan Sugar Cookie Tart Shell, or other tart shell of your choice
• 3 large eggs, cold
• 3 large egg yolks, cold
• 1 1/8 cups sugar
• 1/8 teaspoon salt
• 3/4 cup fresh lemon juice from 2 to 4 lemons
• 1 teaspoon finely grated lemon zest
• 1 stick (8 tablespoons) cold unsalted butter, cut into 8 pieces (see note)
• garnish of choice; a lemon slice and blueberries are nice

Use  large metal bowl over a pot that is slightly smaller than the diameter of the bowl. A tall stockpot works well. Put enough water in the pot to come to about an inch below the bowl when the bowl is placed on the pot and bring the water to a good boil.

Finely grate 1 teaspoon zest from one lemon and set aside. Juice the lemons to get the 3/4 cup (I used two very large and juicy lemons but this may vary) and set aside. Cut butter into chunks and set aside.

Working over the metal bowl and using a metal strainer, add your eggs & yolks to the strainer. Using a rubber spatula, work them through the strainer into the bowl, below. Add sugar & whisk for about 1 minute, or until the mixture is smooth.

Set the bowl over the pot and, using a large whisk, whip the mixture while you turn the bowl (for even heating). After about 2 minutes, when the eggs are foamy and have thickened, add one-third of the lemon juice.

Continue to whisk vigorously and, when the mixture thickens again, add another one-third of the lemon juice.

Whisk until the mixture thickens again, then add the remaining lemon juice. Continue whisking vigorously, still turning the bowl, until the mixture is thickened and light in color and the whisk leaves a good trail as it is run through the mixture.

The total cooking time will vary, but took me about 20 minutes. Don’t be afraid to turn up the heat should it seem as if the mixture isn’t thickening in a timely manner.

Turn off the heat and leave the bowl over the water as you whisk in the butter a piece at a time. The sabayon may loosen slightly, but it will thicken and set as it cools.

Immediately pour the warm sabayon into the tart crust. Leave at room temperature for one hour and then chill for one hour, or longer. Serve at room temperature or cold.

Garnish, if desired with a lemon slice and blueberries or other garnish of your choice.

Notes:

• I have adapted Thomas Keller’s original recipe and I make 1 1/2 x the amount of the filling in my recipe. The larger amount took a longer time whisking than his original 10 minutes. It took nearly 20 minutes.
• In my photos, I used a 10″ tart pan, but in the future, I will use this amount in a 9″ tart pan so the filling will be more substantial.
• Do not stop whisking for more than a second while cooking this custard.
•  I also did not broil the tart.
• Butter may be drastically reduced in the recipe.

Recipe adapted from Thomas Keller