Serves: Makes 2½ cups
- 3 large eggs
- 3 large egg yolks
- 1 cup minus 1 tablespoon (6½ ounces) sugar
- ¾ cup (6 ounces) strained freshly squeezed lemon juice
- 6 tablespoons (3 ounces) cold unsalted butter, cut into ½-inch pieces
Fill the large bowl halfway with ice and water and set it aside. Fill the bottom of the double boiler with 2 inches of water and bring to a rolling boil. Check to see that the water is at least 2 inches below the top portion of the double boiler.
Place the eggs, egg yolks, and sugar into the top of the double boiler (off the heat) and whisk until blended. Add the lemon juice and mix well. Reduce the heat until the water is at a gentle boil. Place the egg mixture over the water and cook, whisking constantly but leisurely, and scraping the edges frequently so the eggs don't scramble there, until the curd is very thick, about 7 minutes. A finished curd should hold its shape; when the whisk is lifted and a bit of curd falls back into the bowl, it should remain distinct on the surface rather than blending back into the mixture, and should register about 180°F on the thermometer. Do not let the curd boil, or you will have bits of scrambled egg in your curd (if this happens, quickly remove the bowl from the heat and continue to the next step).
Immediately strain the curd through the strainer set over the medium bowl. Use the spatula to push the curd through the strainer, leaving behind any bits of scrambled egg. Add the cold butter pieces to the curd, burying them so they melt quickly. Wait 1 minute, then whisk until the butter is completely melted and blended with the curd. Press a piece of plastic wrap directly on the surface of the curd, then set the medium bowl in the large bowl of ice water. Once the curd has completely cooled, use or store in the refrigerator until needed.
Storing: The lemon curd may be prepared up to 3 days in advance and should be consumed within 5 days. Keep the curd refrigerated in an airtight container with a piece of plastic wrap pressed directly on the surface to prevent a skin from forming.