Boil: Wash the potatoes, chop into bite-size chunks and place in a large pot filled with enough cold water to just cover them. Add 1 teaspoon salt and bring to a boil over medium-high heat. Once the water starts boiling, set a kitchen timer to 15 minutes and then check the potatoes to see if they can easily be speared with a fork. If not, boil for a minute or two longer and test again. Once they're done, drain and let cool in your colander.
Prep: Chop the celery, scallions, chives and dill; set aside. Combine the mayonnaise, olive oil, vinegar and mustard in a medium bowl; stir well to incorporate everything.
Combine: Once the potatoes are cool, place everything in a large mixing bowl and stir to combine.
Garnish: Season with salt and pepper, garnish with extra fresh herbs and scallions if desired, and enjoy!