Start grill. Rinse potatoes, do not peel. Pat dry then season with salt and pepper. Place on prepared grill and cook for 20-25 minutes, until desired doneness.
While potatoes are cooking, prepare your hard boiled eggs, if needed. My favorite way to boil eggs is place the eggs in a pot with cold water + 1 T of white vinegar. Bring to a boil, cover and turn off heat then leave in covered pot for 12 minutes. Once cooked, strain, place in bowl in fridge to cool until ready to add with potatoes.
Once potatoes are finished cooking, let cool in fridge until a little below room temperature. Once cool enough, remove from fridge and cut potatoes into quarters. Place quartered potatoes in large bowl.
Roughly chop hard boiled eggs and add to potatoes. I like my egg pieces a little big, but you can chop them as small as you'd like.
Add mayo, sugar, mustard, salt and pepper to potato/egg mixture. Stir together until fully combined - about 2-3 minutes to really make sure the salt and mustard are evenly distributed. Place in fridge until ready to serve.
When ready to serve, sprinkle freshly chopped chives on top and enjoy immediately!