Heat the chicken broth to boiling and keep the broth hot. You will need between 9 to 12 cups of hot chicken broth altogether.
Melt 2 ounces butter over medium heat in a large, heavy stockpot. Add the chopped onion, and saute until the onion is soft and golden, stirring occasionally, about 7 minutes. Add the Arborio rice. Stir well to coat the rice with the butter. Sprinkle with the saffron threads. Cook for one minute, stirring.
Turn heat to medium-high. Add 2 cups of the hot chicken broth, or enough to just cover the rice. Stir continually. When most of the broth has been absorbed, add the cauliflower and stir well. When all boiling broth has been absorbed, add approximately 1/2 cup more boiling broth, stirring until absorbed. Repeat this procedure until the rice is al dente.
Stir the remaining butter into the rice, along with the freshly grated Parmigiano-Reggiano. Adjust texture with additional broth. Taste for seasoning, and serve hot from a large platter onto warmed plates.