Prep time: 10 min
Cook time: 47 min
- 4 tablespoons unsalted butter
- 2 medium-sized yellow onions, chopped
- 1/4 cup unbleached flour
- 3 cups organic whole milk
- 1/4 teaspoon freshly grated nutmeg
- 1 pinch of cayenne
- 1 1/2 cups grated Gruyere cheese
- 3 16 oz. bags of organic, chopped spinach – thawed
- 1/2 teaspoon kosher salt (up to 1 teaspoon)
- 1/4 teaspoon ground white pepper (up to 1/2 teaspoon)
- 2 tablespoons unsalted butter
- 1 1/2 cups panko breadcrumbs
- 1 pinch sea salt, to taste
- Preheat oven to 400 degrees.
- Squeeze the liquid from the thawed spinach, handful by handful. Set aside.
- Heat milk to simmer in saucepan.
- Melt the butter in a heavy-bottomed pot. Add onions and cook until wilted but not browned, about 10 minutes. Add the flour and cook for 2 minutes. Stir in the hot milk and whisk the sauce until it thickens. Add the nutmeg and cayenne. Turn off the heat.
- Stir in the cheese and season with salt and pepper. Taste and correct seasoning. Add the spinach and mix in well.
- Pour into a 9X11 glass or ceramic baking dish. Prepare crumb topping.
- Melt butter in medium skillet. Add panko, sprinkle with sea salt and stir until lightly toasted. This occurs quite suddenly.
- Gently smooth the toasted panko on top of the gratin. Cook for 30-35 minutes until bubbling.