Begin by peeling and slicing the butternut squash into thin rounds, ensuring even cooking. Thinly slice the onion and mince the garlic cloves.

In a large skillet, heat a splash of olive oil over medium heat. Add the sliced onions and minced garlic, cooking for about 5 minutes until they soften.

Layer the thin slices of butternut squash evenly over the sautéed aromatics. Sprinkle nutmeg, salt, and pepper over the squash.

Pour in the heavy cream while gently mixing it with the squash mixture and let it simmer for about 3-4 minutes.

Preheat your oven to 375°F (190°C) and transfer the mixture into a greased baking dish. Sprinkle grated Parmesan cheese on top followed by a layer of breadcrumbs.

Bake for 25-30 minutes, or until the top is golden brown and bubbly.

Remove from the oven and allow it to cool for a few minutes. Sprinkle fresh herbs on top before serving.