- 1 to 2 medium grapefruit, to yield 3/4 cup sections (about 16 small sections) plus juice
- 1 lime, to yield a scant 1/4 cup sections (about 8 sections)
- 2 tablespoons unsalted butter
- 1/2 cup finely diced yellow onion (2 ounces)
- 2 cups Carnaroli or Arborio rice
- 4 to 5 cups chicken stock
- 1/4 cup mascarpone
- Slice both ends off the grapefruit and lime, cutting just deeply enough to expose the juicy flesh. Setting the citrus on a cut end, use a paring knife to carve away the skin and white pith in a series of smooth, curved strokes from top to bottom, rotating the citrus a little with each stroke. If you don't get all the pith on the first go-round, go back and trim any you missed. Working over a bowl to catch juices, cradle the citrus in one hand, slide the blade of the knife close to the membranes on either side of each segment and gently pry out the sections. Tease out any seeds you encounter as you go, and don't worry if some of the sections break. Squeeze the remaining juice from the grapefruit "carcasses" into the bowl.
- Warm the butter in a 4-quart saucepan or another medium pot over medium-low heat. Add the onions and a few pinches of salt. Cook, stirring regularly, until the onions are tender and translucent, about 6 minutes. Add the rice and stir until the grains are warm and coated with fat. Add about 2 cups of the stock, adjusting the heat to maintain a gentle simmer, then stir as needed until it has been mostly absorbed. Add another cup of stock and repeat. The risotto should look like a shiny porridge of pearls. Taste: The rice will still be hard and a little raw tasting. Correct the satiny liquid for salt. Add another 1/2 cup or so of stock and stir as needed until just absorbed. Taste again, checking flavor and doneness.
- Break the citrus sections into irregular pieces as you add them, and the grapefruit juice, to the risotto. Continue to cook as described above. Taste again. If the rice is still quite firm, add more stock about a tablespoon at a time and cook until it is al dente, with a little firmness still in the center. If your grapefruit was very juicy, you may use little of the remaining stock. Turn off the heat and, with a little vigor, stir in the mascarpone. The citrus will be reduced to pretty flecks in the creamy rice. Serve promptly.