01 -
Trim the ends off the grapefruit and lime. Using a paring knife, remove the skin and cut the segments over a bowl, collecting all juices. Remove any tough membrane from the segments. Squeeze the remaining membranes to extract maximum juice.
02 -
In a medium saucepan (4-6 quarts), melt butter over medium-low heat. Add onions with a pinch of salt and cook until translucent, about 5 minutes. Add rice and stir until coated with butter and shiny.
03 -
While preparing the onions and rice, warm the chicken stock in a separate saucepan and keep at a gentle simmer.
04 -
Add about 500ml of warm stock to the rice. Maintain a gentle simmer, stirring occasionally. As liquid absorbs, add another 250ml of stock. Continue adding stock in 125ml increments, stirring regularly to ensure even cooking.
05 -
When rice is nearly cooked, season with salt. Add the citrus segments and juice, gently crumbling the segments as you incorporate them into the risotto.
06 -
Continue cooking and stirring until rice is soft and velvety with no raw taste. The risotto may require between 3.5-5 cups of stock total.
07 -
Remove from heat and stir in the mascarpone until fully incorporated. Serve in soup bowls, mounding the risotto in the center.