Fill a small pot 3/4 of the way with water and bring to a boil. Once boiling, gently drop the eggs in. Boil for 11 minutes and immediately place in a bowl of ice water. This will help with removing the shell.
While the eggs are boiling, wash and scrub the potatoes. Pat dry and cut them into quarters. Place the quartered pieces in another small pot filled with cold water. Bring to a boil and cook for 15-20 minutes, until the potatoes are fork-tender.
Once the shells are removed from the egg, mash them with the yogurt, mayonnaise, lemon juice, and Dijon.
Prepare the chopped vegetables and fold them into the egg mixture. As the potatoes are cooled, slightly mash them and fold them into the mixture as well, adding the spices. Be careful not to over-mix.
Toast your bread. Melt the cheese slightly by placing the provolone slices on the bread while it is still hot.
On top of the provolone, add arugula and the potato egg salad. Garnish with green onions and enjoy!