Cook Spinach Mixture:If using fresh spinach, wash it.In a pan, heat olive oil, add spinach and cook until wilted. Remove from heat.

Make Sauce:In a saucepan, melt butter over medium heat. Add flour and cook, stirring, for about 2 minutes.Gradually whisk in milk until smooth. Cook until thickened, then add salt, pepper, and nutmeg.

Combine Ingredients:Stir the spinach mixture into the sauce. Allow it to cool slightly.Beat the egg yolks and fold them into the spinach mixture.

Fold in Egg Whites:Gently fold in one-third of the beaten egg whites to lighten the mixture.Carefully fold in the remaining egg whites until no white streaks remain.Add cheese to mixture and gently combine.

Prepare Puff Pastry:Roll out the puff pastry sheet to fit the ramekins/baking dish. Place it in the dish, ensuring it covers the bottom and sides.

Assemble and Bake:Pour the spinach mixture onto the puff pastry.Bake in the preheated oven according to the puff pastry package instructions or until the pastry is golden brown.

Serve:Let it cool slightly before serving. The puff pastry will add a flaky and crispy layer to your spinach soufflé.Add Monterey Jack cheese to mixture and stir well to combine.