Add all other ingredients to the large bowl (except the optional fresh spinach, tomatoes, and shredded carrots). Mix together well. Place bowl in refrigerator.
Heat pan or griddle to medium, and add oil or butter. After a minute or so open the hoagie rolls and heat them upside down for a few minutes until they start to brown.
If using spinach and tomato, you can add a layer of spinach onto the bottom of the hoagie roll, then put tomato on. Next add your hearts of palm salad mixture. If using shredded carrots you can add them on top. Enjoy!