roasted stuffed onions

INGREDIENTS

• 10 medium red and yellow onions (4 lb)
• 1 lb sliced bacon, cut crosswise into 1-inch-wide pieces
• 3 celery ribs, cut crosswise into 1/2-inch-thick slices
• 1 teaspoon salt
• 1 teaspoon black pepper
• 3 garlic cloves, minced
• 15 oz baby spinach, trimmed and coarsely chopped (14 cups)
• 1 (9-inch) round loaf country-style bread (1 1/4 lb), cut into 1/2-inch cubes (10 cups), lightly toasted
• 2 cups salted roasted cashews (10 oz), coarsely chopped
• 1 stick (1/2cup) unsalted butter, melted
• 1 1/4 cups turkey giblet stock