Step 1

Melt the butter in a Dutch oven or large saucepan over medium-high heat. Add the shallots and garlic and cook, stirring, until softened, about 2 minutes. Add the spinach in four batches, turning each batch with tongs or a rubber spatula and allowing it to wilt before adding the next.

Step 2

Add the flour and cook, stirring constantly, until no dry flour remains. Slowly stir in the heavy cream and milk. Bring to a simmer, stirring, then reduce the heat to the lowest possible setting and cook, stirring occasionally, until the spinach is completely softened and the sauce has thickened, about 1 1/2 hours.

Step 3

Stir in the nutmeg and crème fraîche and season to taste with salt and pepper. Remove from the heat.

Step 4

If desired, preheat the broiler to high. Transfer the creamed spinach to a 1-quart oval or round casserole dish and top it with the cheese. Broil until the spinach is bubbly and the cheese has formed a well-browned crust, about 2 minutes. Serve.