Spinach Gratin

INGREDIENTS

• 3 16 oz. bags of organic, chopped spinach - thawed
• 1/2 to 1 teaspoon kosher salt
• pinches of cayenne
• 2 tablespoons unsalted butter
• 4 tablespoons unsalted butter
• 1/4 cup unbleached flour
• 3 cups organic whole milk
• sea salt, to taste
• 1 and 1/2 cup panko breadcrumbs
• 2 medium-sized yellow onions, chopped
• 1/4 to 1/2 teaspoon ground white pepper
• 1/4 teaspoon freshly grated nutmeg
• 1 and 1/2 cup grated Gruyere cheese