Boil the eggs. Once the water reaches a boil, cook for 10 minutes, then they will be ready.

Once the eggs are cool, cut them in half and remove the yolks, adding them to the chopped mussels.

Make a béchamel sauce by melting the butter in a saucepan with a little olive oil. Add the flour and stir until dissolved.

Add enough milk to create a creamy texture, sprinkle with nutmeg and salt, and finally, add the pickling liquid from the mussels. Mix well.

Fill each egg half with the mixture until all are filled.

Pour the remaining béchamel over the eggs, sprinkle with thyme, grate cheese on top, and place the tray in the oven. Broil until golden brown.