Ingredients
3 cups sugar
2 tablespoons finely grated mandarin-orange zest (from 9 oranges), plus 1 1/2 cups fresh juice (from 13 oranges)
1 tablespoon finely grated lime zest (from 2 limes), plus 3/4 cup fresh juice (from 5 limes)
18 large egg yolks
3/4 teaspoon kosher salt
3 3/4 sticks cold unsalted butter, cut into small pieces
Preparation
In a medium saucepan, whisk together sugar, both zests, and egg yolks; whisk in citrus juices and salt. Add butter; place pan over medium-high and cook, whisking constantly, until butter has melted, mixture is thick enough to coat the back of a spoon, and bubbles form around edge of pan, about 11 minutes (do not let boil).
Remove pan from heat immediately. Pour curd through a fine-mesh sieve into a glass bowl. Press plastic wrap against surface of curd; refrigerate until cool. Transfer to 6 seven-ounce jars; curd can be refrigerated in jars up to 2 weeks.
