In the blender, place the milk, eggs, flour, sugar, and salt, and blend for a few seconds until everything is mixed. Add the melted butter with the machine running slowly and blend until smooth. Transfer to a bowl and refrigerate for at least 1 hour or overnight.

Remove the mixture from the refrigerator for about 30 minutes before making the crepes, and beat with a whisk for 30 seconds.

Heat a nonstick pan about 23-25 cm in diameter over medium-high heat until water droplets dance and jump before evaporating. Add ¼ cup or 60 ml or half a ladle of batter into the pan, turn the pan so that the mixture coats the entire bottom, and cook 45-60 seconds when the edges begin to brown and slightly lift with the help of a spatula to turn the pancake and cook another 45 seconds. Stack cooked crepes on a plate and keep them covered with a clean kitchen towel.

Bring salted water to boil in a medium saucepan over high heat. Drop the spinach and wait to return to a boil. Cook for 4 minutes—strain and press with a spoon to remove as much water as possible. Cut small. Mix the ricotta and grated cheese in a large bowl. Add the spinach, stir well, and season to taste with nutmeg, salt, and pepper. Use three tablespoons of filling per crepe. Line them up in a dish that can go in the oven.

Melt butter in a medium saucepan over medium heat. Add the milk, water, salt, and diluted cornstarch. Cook over medium heat, stirring until it boils. Reduce heat and simmer for 2 minutes, continuously stirring. Season with nutmeg, pepper, and salt to taste.

Pour over stuffed crepes and bake for 20 minutes at 300F or 150C. Serve hot.