Start by peeling the starchy potatoes and chop them into evenly sized chunks. Place in a large pot with cold water and a pinch of salt. Bring to a boil and cook for 15-20 minutes until fork-tender. Drain and cool slightly before mashing.

In a separate bowl, combine the mayonnaise, sugar, vinegar, and mustard if desired. Whisk until smooth and creamy, adjusting the taste as necessary.

Fold the warm, mashed potatoes into the dressing until well-coated. Add chopped vegetables and boiled eggs if using. Mix gently to avoid overworking the potatoes.

Transfer to an airtight container and refrigerate for at least 30 minutes to allow flavors to meld.

Stir gently before serving. Present in a bowl and garnish with fresh herbs if desired.