Preheat your oven to 400°F (200°C).
Brush the cut sides of the squash with olive oil and sprinkle with salt, pepper, and optional nutmeg.
Place the squash halves cut side down on a baking sheet lined with parchment paper.
Roast for 30-35 minutes, or until the flesh is tender and easily pierced with a fork.
While the squash is roasting, prepare the spinach. If using fresh spinach, blanch it in boiling water for 1 minute, then drain and squeeze out excess moisture. If using frozen spinach, ensure it’s thoroughly thawed and drained.
In a large skillet, melt the butter over medium heat. Add the minced shallot and garlic, sautéing until fragrant (about 2 minutes).
Stir in the spinach, breaking it up and mixing it with the aromatics.
Pour in the heavy cream, stirring until the spinach is coated.
Add the Parmesan, cream cheese, and nutmeg, stirring until the mixture is smooth and creamy. Season with salt and pepper to taste.
Turn the roasted squash halves cut side up and fill each cavity generously with the creamed spinach.
Mix the panko breadcrumbs with melted butter and Parmesan cheese, then sprinkle over the spinach filling.
Return the squash to the oven and bake for an additional 10-15 minutes, or until the topping is golden and crisp.
Allow the squash to cool for 5 minutes before serving. Garnish with fresh herbs like parsley or thyme for a pop of color.