Heat 2 Tbsp. butter in medium pan. Thinly slice the onion; sauté in the butter for about 5 minutes, or until clear and cooked.

Leaving the (24) rolls attached, horizontally slice the top off; set aside. Place the bottom (attached 24 pieces) rolls in a 9×13 foil-lined baking pan. (You may need to squeeze them into the pan, or remove a row if you choose.)

Spread the pesto evenly over the bottom bread.

Next layer on top of the pesto the turkey, sautéed onions, and cheese slices.

Place the top section of the rolls that you already removed back on top of the sandwich.

In a medium sauce pan bring the 1/2 cup butter to a soft boil. Add mustard, worcestershire, poppyseeds, and brown sugar.

Pour sauce over the 9×13 sandwiches.

Cover with foil and bake at 350 for 20. Remove foil and bake another 10 minutes.

Serve hot or cold.