Coat the chicken tenders in the ranch seasoning mix and cook the tenders in a small pan. After it's completely cooked, cool a little bit and chop it in the small bits.
Mix the cooked, chopped chicken, cream cheese and mozzarella cheese together, until all combined.
Cut the French dough into 8 pieces. Flatten the dough into circles. Scoop some chicken mixture in the centers of the flattened dough. Don't stuff them too much or the dough will rip.
Pull together the opposite ends of the circle and press it together firmly. Work your way down the sides, pressing the dough firmly together.
Place pirojki onto the greased baking pan. Whisk the egg and brush pirojki, lightly but evenly.
Bake pirojki for 15-17 minutes, until golden brown.