4 cups low-sodium chicken or vegetable broth
3 medium beets (about 1 pound)
2 tablespoons unsalted butter
2 tablespoons olive oil
1 medium onion, finely chopped
3 1/2 teaspoons kosher salt, divided
1 1/4 teaspoons freshly ground black pepper, divided
1 1/2 cups arborio or carnaroli rice
4 teaspoons white wine or Champagne vinegar, divided, plus more
3 tablespoons heavy cream
4 tablespoons coarsely chopped parsley, divided
2 ounces fresh goat cheese, crumbled (optional)
Bring broth and 5 cups water to a boil in a large pot over high heat. Reduce heat to low and gently simmer.
Meanwhile, peel beets, then coarsely shred using a food processor fitted with the shredder attachment or the large holes of a box grater.
Heat a large wide pot or sauté pan over medium-high. Cook butter and oil, stirring occasionally, until butter melts. Add onion and sauté until softened and translucent, about 5 minutes. Add beets, 1 tsp. salt, and 1/2 tsp. pepper and sauté until tender, about 10 minutes more.
Add rice and cook, stirring constantly, about 2 minutes, then add 1 1/2 cups broth, 3 tsp. vinegar, and 1 tsp. salt. Reduce heat to medium and simmer, stirring constantly, until liquid has evaporated. Continue adding broth, 3/4 cup at a time as rice absorbs liquid, stirring constantly and simmering until rice is tender, 30–40 minutes; season with 1 tsp. salt and 1/2 tsp. pepper halfway through. About 2 minutes before rice is al dente, add cream, 2 Tbsp. parsley, remaining 1 tsp. vinegar, 1/2 tsp. salt, and 1/4 tsp. pepper.
Divide among 4 plates or bowls, then top with goat cheese, if using, and remaining 2 Tbsp. parsley.