2 cups vegetable broth
2 cups water
7 tablespoons extra-virgin olive oil
1 leafy sprig fresh rosemary
2 navel oranges
1/2 cup finely chopped onion
1 1/2 cups Arborio or Carnaroli rice
1 cup freshly grated Parmigiano-Reggiano or Grana Padano cheese
1/4 teaspoon fine sea salt
Combine broth and water in a medium saucepan; heat to a very gentle simmer.
Meanwhile, combine 5 tablespoons oil and rosemary sprig in a small saucepan; heat over low heat until oil reaches a bare simmer, about 2 minutes. Remove from heat and let stand 10 minutes, then remove rosemary from oil; reserve oil. Remove and reserve leaves from toasted rosemary; discard stem.
Finely grate zest from 1 orange; put zest in a small bowl or ramekin and cover with plastic wrap.
From remaining orange, using a sharp paring knife, cut zest in long strips, avoiding white pith. Thinly slice zest strips lengthwise. Wrap sliced zest strips in plastic wrap; set aside grated zest and strips.
Heat remaining 2 tablespoons oil in a large saucepan over medium heat. Add onion; cook, stirring frequently with a long handled wooden spoon, until softened, about 3 minutes.
Add rice, increase heat to medium-high, and cook, stirring frequently, until rice is translucent, about 4 minutes. Add 1 cup broth mixture, reduce heat to medium-low and cook, stirring frequently, until liquid is mostly absorbed.
Add about 1/2 cup broth and grated zest. Cook, stirring constantly, until broth is mostly absorbed. Continue adding broth in 1/2 cupfuls, stirring constantly, and allowing each addition to mostly absorb before adding the next, until rice is tender yet firm to the bite (you may have broth left over).
Remove risotto from heat. Stir in cheese, 1 to 2 tablespoons reserved rosemary oil and salt. Adjust seasoning to taste. Serve risotto immediately, sprinkled with reserved zest strips and rosemary.