Put butter and olive oil in a high rimmed pan or pot over medium heat. When the butter melts,add chopped onions to the melted butter and saute for about 3-4 minutes over medium heat.
Meanwhile, heat chicken broth in another medium pot. You want to have the broth hot, but not boiling or even simmering.
Add the arborio rice to the sauteed onions and stir continuously for 3 minutes.
Add white wine, and cook, stirring continuously, until the wine is fully absorbed into the rice. Substitute additional chicken broth if desired.
Stir in pumpkin puree, grated Romano cheese (or Parmigiano-Reggiano), and light cream. Cook for just a minute or two more, stirring continuously, until the cream is fully absorbed and the pumpkin clings to the rice.