Melt the butter over medium-high heat in a large frying pan.
Add the onion and salt and cook, stirring occasionally, until softened, about 5 minutes
Add the sage and cook, stirring, for 30 seconds.
Add the rice, stir to coat with the butter, and cook for a minute or two, until becoming translucent.
Pour in the wine. Cook, stirring frequently, for a minute or two until mostly absorbed.
Stir in about a cup and a half of the broth, along with the nutmeg, cayenne, and pepper. Cook, stirring frequently but not constantly, until broth is mostly absorbed. Continue in this manner, adding more broth as it absorbs into the rice, until you've used all but ½ cup of the broth.
While the risotto simmers, combine the pumpkin, maple syrup, cream, and remaining ½ cup broth in a blender or food processor. Process until completely smooth.
Add pumpkin puree to pan and cook, stirring occasionally, until most of the broth is absorbed. Risotto is finished cooking when each grain of rice is tender but still has a nice hint of chewy bite, and there's still some delicious starchy broth remaining. Keep in mind that the broth will thicken as it cools.
Stir in parmesan.
Rest the risotto for five minutes before serving.
Spoon into wide, shallow bowls and garnish with balsamic glaze and roasted pumpkin seeds if you like.