1 6–8 pound Cinderella, cheese, or Jarrahdale pumpkin
1/4 cup (1/2 stick) unsalted butter, softened
1 teaspoon fennel seeds, finely ground
2 large pinches piment d'Espelette
Kosher salt and freshly ground black pepper
2 cups (packed) grated Gruyère
1 cup fresh breadcrumbs made from white bread
2 garlic cloves, thinly sliced
2 fresh or dried bay leaves
5–7 cups low-salt chicken stock
Flat-leaf parsley