Preheat the oven to 350°F
Roast the squash as described in the text.
Make the bread crumbs by pulsing two generous handfuls of torn bread in the food processor with a teaspoon or so of olive oil, dried parsley and a tablespoon of manchego cheese. Add salt and other seasonings to taste.
Saute the onions and the thyme in a small amount of olive oil until the onions have softened and changed color.
When ready to bake, combine the squash, onions, hazelnuts and remaining cheese in a large mixing bowl. Season to taste.
Transfer to a baking dish and top with the bread crumbs.
Bake for 20 minutes or until the bread crumbs are crunchy and the casserole is bubbly.