Preheat oven to 375°F (190°C). Lightly grease a baking dish.

Melt 2 tbsp butter in a large frying pan over medium heat.

Add chopped shallot and cook for 3-5 minutes, until softened.

Add baby spinach and cook, tossing, for 5 minutes, until wilted. Remove spinach from pan, reserving the liquid.

Add the remaining 2 tbsp butter to the pan. Once melted, add flour and cook for 2 minutes, stirring occasionally.

Whisk in milk until smooth, then add heavy cream, nutmeg, Parmesan cheese, spinach, and reserved liquid. Season with salt and pepper to taste.

Transfer the mixture to the prepared baking dish and bake for 15 minutes, or until bubbly.

Preheat broiler.

Sprinkle fresh breadcrumbs over the spinach mixture.

Broil until golden brown and crunchy.