Preheat oven to 425°F.
In high-sided ovenproof skillet set over medium-high heat, add 2 tbsp butter and onion; cook for 2 to 3 mins or until softened. Add rice (discarding bag); stir until well coated. Add broth; stir for 1 to 2 mins or until almost totally absorbed. Add cream; bring to boil. Cover and transfer to oven. Bake for 8 to 10 mins or until rice is tender.
Meanwhile, on rimmed baking sheet toss together pumpkin, remaining butter, sage, salt and black pepper. Bake, stirring halfway through, for 8 to 10 mins or until tender and browned.
Stir pumpkin and Parmesan cheese into risotto. Serve immediately.
Serve with freshly ground black pepper, fried sage and crushed pistachios sprinkled over top for a tasty and impressive presentation.