Preheat and Prepare: Preheat your oven. Lightly butter a medium-sized pre-seasoned cast iron skillet.
Sage Preparation: On the stovetop, set to medium-high, quickly brown the sage leaves in the skillet, add white onion and cook until translucent then remove from heat.
Prepare Vegetables: Peel and chop the pumpkin into small chunks. Place in the bottom of a steamer basket, with cauliflower florets on top. Steam over boiling water. Take out the cauliflower after 3 minutes and place in the baking dish. Keep steaming the pumpkin until it’s very soft, about 15 minutes.
Make Sauce: When the pumpkin is soft, blend it in a blender with cream, pepper, chili, paprika, sage leaves, onion and garlic until smooth. Occasionally scrape down the sides.
Heat Sauce: Transfer the sauce to a small saucepan over medium heat. Add half of the grated cheese, stirring until it melts completely. Adjust seasoning with salt and coarse pepper to taste.
Combine and Coat: Pour the sauce over the cauliflower in the cast iron pan and gently toss to coat. Sprinkle the remaining cheese on top.
Bake and Serve: Bake for 30 minutes or until the cauliflower is tender and the top is golden. Serve immediately.