This is the risotto that shows up the moment the weather turns, without anyone actually deciding it should -- my mother simply starts making it again once the squash at the market looks right, and that's the entire signal the rest of us need.
Serves 4.
Toss half the diced squash with a little olive oil and salt, and roast at 220°C (425°F) until tender and lightly caramelized at the edges, about twenty minutes. Set this portion aside for garnish.
Meanwhile, simmer the other half of the squash directly in the warm broth until soft enough to mash easily, about ten minutes. Puree it right into the broth with an immersion blender, or mash it well with a fork -- this is what gives the finished risotto its color and body from within, rather than relying on squash pieces alone to carry the flavor. Keep the broth warm.
Warm a little butter in a wide pan, and cook the onion gently until soft. Add the rice, and toast for two to three minutes. Pour in the wine, and let it cook off entirely.
Begin adding the squash-enriched broth, a ladle at a time, stirring often and waiting for most of each addition to absorb before adding more. Continue for sixteen to eighteen minutes, until the rice is tender with a slight bite remaining.
Remove from the heat, and beat in the remaining butter and the Parmigiano until glossy. Season with salt and a generous amount of black pepper -- the squash's sweetness wants real seasoning to balance it, more than you might expect. Meanwhile, fry the sage leaves briefly in a little butter or oil until crisp. Top each portion with the roasted squash and a few crisp sage leaves.
If the risotto tastes thin and watery despite all that squash, it was used only as a garnish rather than pureed into the broth itself -- that puree is doing most of the actual work here, not the roasted pieces on top. If the dish tastes one-note and overly sweet, it needed more salt and pepper to balance the squash's natural sugar; season more assertively than feels instinctive. And if the texture comes out gluey rather than creamy, a pre-made squash puree was likely substituted for the two-stage technique above, which builds flavor and texture in a way a shortcut simply can't replicate.
A little girl once declared, loudly enough for half the dining room to hear and laugh, that the risotto alla zucca was "better than candy," which her parents found equal parts mortifying and completely accurate. She ordered it every autumn for years after that, without fail, until the visits gradually thinned out the way they do as children grow up and stop being brought places by their parents.
She reappeared perhaps fifteen years later, unmistakably the same person grown into an adult, with a small child of her own in tow, and ordered two bowls before she'd so much as glanced at the rest of the menu.