Creamy Potato Salad: Grandma's Secret (Almost!)

Ingredients

• 2 lbs (900g) Yukon Gold potatoes, or other waxy potatoes, peeled or unpeeled, and cut into 1-inch cubes
• 1 cup (240ml) mayonnaise (full-fat or light)
• 1/4 cup (60ml) sour cream or Greek yogurt
• 2 tablespoons yellow mustard (American or Dijon)
• 2 tablespoons apple cider vinegar (or white wine vinegar)
• 1 tablespoon finely chopped fresh dill (or 1 teaspoon dried)
• 1 teaspoon celery seed (optional)
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 1/2 cup (50g) finely chopped celery
• 1/4 cup (25g) finely chopped red onion
• 2 hard-boiled eggs, peeled and chopped (optional)