Amish Potato Salad

INGREDIENTS

• 6 medium white potatoes with skin
• 1 small onion, finely chopped
• 1 cup chopped celery
• 1 cup chopped carrots
• 1 teaspoon celery seed
• 4 hard-cooked eggs, peeled and chopped
•  
• 2 eggs, beaten
• 3/4 cup white sugar
• 1 teaspoon cornstarch
• 1/2 teaspoon salt
• 1/3 cup apple cider vinegar
• 1/2 cup milk
• 1 teaspoon prepared yellow mustard
• 3 tablespoons butter
• 1 cup mayonnaise or salad dressing