Heat oven to 400 degrees F. Coat a large baking sheet with nonstick cooking spray.
In a small bowl, mix together cheeses and chili powder. Set aside.
Place pastry sheet on a lightly floured work surface. Roll out to a 12 x 10-inch rectangle. Lightly brush with egg wash. Starting at a short end, sprinkle 3/4 cup of the cheese mixture over one half of the pastry. Fold other half over cheese like a book. Gently press down over cheese. Place on a small baking sheet and refrigerate for 15 minutes.
Place pastry on a cutting board and trim sides even. Cut into approximately fifty 1-inch squares. Lightly brush tops with egg wash and sprinkle on remaining cheese. Gently press cheese down so it adheres to pastry. Bake at 400 degrees F for 13 to 15 minutes, until golden. Serve immediately.