Blend 1/2 cup milk, 1 teaspoon table salt, 1/4 cup granulated sugar, 1 tablespoon cornstarch, 1/4 cup vinegar, and 1 egg in a blender, food processor or with a whisk until smooth. Add 2 tablespoons butter and 1/4 cup onion.
Pour into a 2 quart batter bowl. Microwave on HIGH for 4-5 minutes, whisking well after every minute (important so the sauce will cook evenly). Mixture should be thick like pudding.
Assembling the Salad
Add 3/4 teaspoon celery seed and 1/4 cup mayonnaise to the cooked dressing. Whisk till smooth. Fold in 1/4 cup sweet pickle relish, 3 hard-cooked eggs, and 7 medium potatoes. Garnish with smoked (or regular) paprika and chill. Serves 6
Notes
Do you have smoked paprika in your refrigerator? If not, use regular paprika. However, the smoked paprika adds a subtle bacon flavor that is delicious. Good on deviled eggs, too.