Preheat the oven to 475°F (250°C). Line a baking sheet with parchment paper.
Melt the butter in a small frying pan over medium heat. Add the sage leaves & cook, stirring occasionally, until the butter is golden & the mixture is fragrant.
Cut the peeled squash in half crossways & place the top half of the squash in a spiralizer; have a plate or a tray to catch the squash. Spiralize the squash. Remove the seeds & spiralize the remainder of the squash. You can also use a peeler or cut squash into thin slices; if you do this, you’ll have to adjust the cooking time.
Place the squash on the baking sheet. Sprinkle with salt & pepper. Add half the sage butter, with the leaves & toss to combine. Top with prosciutto, garlic, almonds & extra sage leaves. Roast for 15 minutes until the squash is tender but al dente. Drizzle with remaining melted butter mixture.
Serve the squash topped with parmesan & extra sage leaves.