Place the potatoes in a large pot. Cover with cold water and add a small handful of salt.
Bring the water to a boil and cover with a lid. Cook the potatoes for at least 15 minutes or until very tender.
Make dressing. In a large bowl whisk together mayo, dijon mustard, whole grain mustard, vinegar, garlic powder, onion, dill, sugar, celery and cayenne pepper. Make sure to season with salt and pepper.
Once potatoes are cooked all the way, drain them and allow them to cool for 10-15 minutes.
You can cut your potatoes even smaller at this point or leave them quartered for a very chunky potato salad.
Mix the warm potatoes, hard boiled eggs and the dressing together. You may add some more mayo at this point depending on how creamy you like it. Season everything with salt and pepper.
Place in the refrigerator for at least 2 hours or overnight.