Spinach Loaf

INGREDIENTS

• 1 cup whole milk
• 3 pounds spinach leaves
• 2 tablespoons unsalted butter, at room temperature, plus extra for greasing the pan
• 4 hard boiled eggs, peeled
• 3 large eggs, at room temperature, beaten
• Four 3/4-inch-thick slices rustic bread, crusts removed, torn into 1-inch pieces
• 1 small onion, chopped
• 1 teaspoon freshly ground black pepper
• 1 1/2 teaspoons kosher salt
• 1/2 teaspoon ground nutmeg
• 1 cup grated Parmesan