Heat chicken broth in a saucepan and keep warm.
In a large saucepan, heat 3 Tbsp. butter over medium heat. Add onion and cook until translucent, 3 to 4 minutes. Add rice, fresh pumpkin and nutmeg. Stir for about a minute, making sure all rice is coated in butter. Add 1 cup chicken broth, stirring well; reduce heat to low. Once broth is incorporated, add 1/2 cup more broth, stirring constantly. Continue to add broth in 1/2 cup increments as rice absorbs liquid, until rice is cooked. Rice will take about 25 minutes to cook and should be creamy but al dente when done.
In last few minutes of cooking, stir in canned pumpkin and maple syrup.
Remove risotto from heat and stir in remaining 2 Tbsp. butter, Parmesan, sage, salt and pepper. Let rest a few minutes before serving.