Spread the peanut butter onto 1 slice of bread, and top with the sliced banana, and the remaining slice of bread.
Butter both sides of the sandwich and place it into the hot pan. Grill for 2 minutes before flipping and grilling for an additional 2 minutes or until the sandwich is golden brown on both sides.
Remove the sandwich from heat and allow it to cool down to room temperature before packing it into a lunch container with veggies.