Cut each hard boiled egg in half vertically, so that you have two symmetrical pieces. Use a spoon to gently remove all the yolks.
Place yolks in a medium mixing bowl, and smash them with a fork. Add mayonnaise to the egg yolks and continue to smash the yolks and mayo together until desired consistency is reached. (You want them pretty smooth so you can pipe them.)
Add the spinach to your yolk mixture, and stir to evenly combine. Season with salt and pepper, to taste, and stir once more.
Transfer yolk mixture to a piping bag with a end cut off (or ziploc bag with one bottom corner cut off). Carefully move the yolk mixture down to the end of the bag, and then squeeze enough yolk mixture into the cavity of each egg to fill it.
Garnish each egg with a small dab of sun dried tomato pesto (just under 1/8 of a teaspoon - the pesto has a very concentrated flavor and is potent. AKA a little goes a long way) and place one chive on top of each egg. Cover and keep refrigerated until ready to serve.