
Start making the sauce. Melt 3 tablespoons of butter in a frying pan over medium heat. Add the flour and stir until smooth. Cook, stirring, until the mixture becomes lighter in color. This will take about 1-2 minutes. Remove the pan from the stove, add the milk, salt and nutmeg. Return to medium heat and bring to a boil, stirring constantly. Then turn off the heat and cool the sauce slightly, stirring.

Defrost the spinach. Heat a deep frying pan with the remaining butter over medium heat. Add the spinach and, covered, simmer for about 3 minutes. Stir and continue simmering without a lid for about 2-3 minutes. Drain off excess liquid and cool slightly, then squeeze the spinach well.

Mix the sauce with the spinach. Heat the sauce over low heat without bringing it to a boil, then stir in the whole egg and egg yolks. Cook, stirring, until the sauce thickens. Add the defrosted spinach and heat through. Season with salt and pepper as needed.