Put cheeses, onion, eggs, cumin, nutmeg, and pepper in the food processor. Pulse till well mixed.
Add spinach and pulse a few times.
Cut puff pastry into 5x5 squares for a large breakfast or meal-size serving. For appetizer or snack, cut puff pastry into.
2 1/2x5 inch strips.
Fill each square with approximately 2 tbsp filling in the middle. Fold pastry over to create a triangle. Pinch sides very well with your fingers, so that filling won't escape. For the smaller strips, use 1-2 tsp filling on bottom half of strip and fold strip over to make a square. Seal well.
Brush each one with milk and sprinkle sesame.
Bake approximately 20 minutes on ungreased cookie sheet, or until browned & puffed up.