Pre-heat your oven to 400 degrees. Line a rimmed baking sheet with foil and set aside.
Let’s start with the squash. Using a very sharp knife, remove the very top (including the stem) and bottom of the squash. Slice the squash in half, and then scoop out the seeds and any stringy bits from the inside of each half. Rub each cleaned half with 1 teaspoon olive oil and season with sea salt and pepper. Place the squash halves cut-side down on the prepared baking sheet and roast for 1 hour until the squash is very tender.
Meanwhile, place the quinoa in a small saucepan with 1¾ cups vegetable stock. Bring to a boil, then lower to a simmer, cover and cook for 15 minutes until all the liquid has been absorbed. Let rest for 5-10 minutes, covered, then fluff with a fork.
Arrange the quartered sprouts on a baking sheet (or in a skillet) and drizzle with 1 tablespoon olive oil and maple syrup. Season with salt and pepper and toss to coat. Roast for 20 minutes, tossing once halfway through until just tender and caramelized. (I like to do this during the last 20 minutes of the squash roasting time to keep things simple.)
Heat a medium saucepan over medium-high heat. Add the pancetta and cook for about 5 minutes until brown and crispy. Reduce the heat to medium-low and add the shallots and garlic. (Makes sure to wait for the pan to cool down or you’ll burn the garlic!) Cook for 2-3 minutes until the shallots become translucent and the garlic is fragrant.
Once the squash is cooked, spoon the insides into a blender or food processor. Add ¼ cup vegetable stock and 1/8 teaspoon ground cinnamon, and puree until smooth.
Place the cooked quinoa to a large mixing bowl. Add the roasted Brussels sprouts, the pancetta mixture, 1½ cups of the kabocha squash puree (you will have a little leftover puree!), 1 cup grated Fontina, ¼ cup Parmesan, and the remaining ¼ cup vegetable stock. Mix until well combined. Taste and season generously with salt and pepper.
Transfer the mixture to a medium casserole dish or cast iron skillet and smooth into an even layer. Top with the remaining ¾ cup Fontina, ¼ cup Parmesan and breadcrumbs. Bake for 20-25 minutes until the cheese is bubbling and lightly browned. Serve immediately.