Method:

Prepare the Spinach: Wash the spinach thoroughly and boil it for about 3 minutes in salted water. Let it cool, then squeeze out any excess water. Blend the spinach until smooth.

Make the Sauce: In a medium-sized saucepan, melt the butter over medium heat. Add the flour and stir to create a roux. Gradually add the milk while stirring to prevent lumps, and cook until the mixture thickens. Season with salt.

Combine the Spinach and Eggs: Once the sauce has thickened, remove it from the heat. Stir in the egg yolks one at a time, followed by the blended spinach and grated Parmigiano Reggiano. Season with more salt if necessary.

Whisk the Egg Whites: In a separate bowl, whisk the egg whites until they form stiff peaks. Gently fold the egg whites into the spinach mixture, being careful not to deflate the air.

Prepare the Ramekins: Grease the ramekins with butter and breadcrumbs. Pour the spinach mixture into the ramekins, filling them about three-quarters full.

Bake: Place the ramekins in a baking dish filled with hot water, making sure the water reaches halfway up the sides of the ramekins. Bake in a preheated oven at 300°F (150°C) for about 40 minutes or until set and golden.

Serve: You can serve the flan on its own or with a side of freshly grated horseradish for added flavor. If you want, you can make crispy potato chips as a garnish.

Tips:

For Vegetarians: This recipe is naturally vegetarian. You can also use plant-based milk (almond or oat milk) to make it dairy-free.

For a Gluten-Free Version: Skip the breadcrumbs for greasing, and instead use gluten-free breadcrumbs or simply grease the ramekins with butter.

Variation: Feel free to add a touch of nutmeg to the spinach mixture for a warm, aromatic flavor.