If frozen, thaw the puff pastry at room temperature for 40 minutes. Preheat oven to 375F and line a baking sheet with parchment paper. In a small bowl, combine the poppy seeds, sesame seeds, dried onion flakes, and steak seasoning.
Lightly flour your hands, the surface you want to roll the pastry out on, and your rolling pin. Roll out the pastry to a rectangle slightly over 16 inches wide and 8 inches tall and trim the edges so you have straight lines. Lightly flour the top of the pastry and cut the rectangle into 4 pieces, each about 4 inches wide and 8 inches tall.
Fold each piece of pastry in half, bringing the two farthest sides together. Use a knife to cut strips (about 1/4 to 1/2 inch wide and 2 inches tall) along the edge of the dough through both layers; be careful not to press the layers of dough together too much.
Lay pastries out on a baking sheet lined with parchment paper. Place 1 oz cheese in the center of each pastry; bring the right strip farthest from you across the cheese, then bring the left strip farthest from you across the first strip. Continue alternating strips this way, making sure that each strip overlaps the previous. Repeat this process on the remaining pastries. Lightly press down on the top of each pastry to help seal the strips together.
Brush the tops of the pastries with eggwash (you will have extra eggwash), then sprinkle 1/2 tsp of the poppy seed mixture on top of each pastry. Bake about 25 minutes, or until puffed and golden.