2 cups chopped fresh rhubarb (about 6 stalks)
1 vanilla bean
3 strips orange peel, roughly 3 inches by 1 inch
½ medium beet, peeled
¾ cup sugar, divided
4 large egg yolks
2 large eggs
2 tablespoons freshly squeezed lemon juice
½ teaspoon salt
6 tablespoons unsalted butter
1½ teaspoons elderflower liqueur, such as St. Germain (optional)
Put the rhubarb in a medium saucepan with enough water to cover it by about ½ inch. Split the vanilla bean with a paring knife and scrape the seeds into a small bowl. Add the vanilla bean pod, the orange peel, the beet half and ¼ cup sugar to the pot. Bring to a simmer over medium heat and cook, stirring occasionally, until the rhubarb has mostly disintegrated, about 15 minutes. Remove and discard the vanilla pod, orange peel and beet, and press pulp against a metal strainer placed over a large measuring cup to extract as much liquid as possible. Discard the solids.
Bring a medium pot of water to a simmer over medium heat. Put the remaining ½ cup sugar, the egg yolks, the eggs, the lemon juice, the salt and the reserved vanilla seeds in a medium steel or glass bowl that will fit over the pot; whisk to combine. Gradually whisk in 1¼ cups of the rhubarb juice (reserve any extra for cocktails or another use), then set the bowl over the simmering water. Cook, beating constantly with a whisk, until the mixture has thickened enough to loosely coat the back of a wooden spoon, 8-10 minutes.
Remove the bowl from the pot and whisk in the butter, 1 tablespoon at a time, waiting until each pat has melted before adding the next. Whisk in the elderflower liqueur, if using. If the curd seems lumpy, strain it through a mesh sieve. Allow to cool and then refrigerate until chilled, at least 4 hours, before serving. Store leftover curd in an airtight container in the refrigerator for up to a week.
Makes 2 cups.
J. Bryan Lowder, Slate