Place each chicken breast half between two sheets of heavy plastic wrap; pound with the flat side of a meat mallet until 1/8 inch thick. Season with salt and pepper; set aside.

In a large skillet cook spinach and onion in hot oil until onion is tender. Remove from heat. Stir in cream cheese until blended. Stir in mozzarella cheese, feta cheese, cheddar cheese, egg yolk, flour, nutmeg, and cumin. Place about 1/4 cup of the spinach mixture on each chicken breast half; roll up jelly-roll style (it's not necessary to seal ends).

Place one sheet of phyllo on work surface (keep remaining sheets covered with plastic wrap to prevent drying out). Brush with some of the melted margarine or butter. Place another phyllo sheet on top of first; brush with margarine. Place one chicken roll near a short side of the phyllo; roll chicken and phyllo over once to cover chicken. Fold in long sides; continue rolling from short side. Place in a shallow baking pan. Repeat with remaining chicken, phyllo, and margarine. Brush with margarine. Bake, uncovered, in a 350 degree F oven for 30 to 35 minutes or until chicken is no longer pink. Makes 8 servings.

Prepare chicken rolls; cover and chill up to 8 hours. Wrap and phyllo and bake as above.

use 32, 14x9-inch sheets. Overlap 2 sheets slightly to make one approximately 18x14-inch rectangle. Continue layering sheets as above.