Cook the spinach until it is soft. Drain it well. (With frozen spinach, just defrost it in the microwave and squeeze it out well).

Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius).

Mix the spinach together with the egg yolks, flour, baking powder, salt, pepper, nutmeg, and three tablespoons of soy milk. (The rest of the soy milk will be used in the mushroom layer.) Whip the egg whites until they are stiff and carefully fold them into the spinach mixture.

Lay a sheet of Gefen Parchment Paper on a baking sheet and oil it well. Sprinkle flour all over the sheet of baking paper and then spread the spinach mixture into a rectangular shape. Bake for 20–30 minutes. Lift a corner of the paper to see if the spinach layer has solidified. Do not over-bake.

Heat the oil in a medium frying pan over a medium-high flame. Add the onion and sauté it until it is translucent. Add the mushrooms and sauté for a few more minutes, until they are soft. Lower the flame and add the salt, pepper, soup mix, and flour. Add the soy milk and stir the mixture until the flour is completely absorbed. You may have to use only half a cup.

The minute the spinach mixture comes out of the oven, smear the mushroom layer all over it evenly, and carefully roll it up while removing the parchment paper from the bottom of the spinach layer. Refrigerate until it is time to serve. Wrap the roll in foil before warming it up. It’s beautiful brought to the table whole on a rectangular platter.