Homemade Salad Dressing
In large bowl, toss together cabbage, onions, celery, carrot, fennel and red pepper. (Make-ahead: Cover with damp towel and plastic wrap. Refrigerate for up to 8 hours.)
DRESSING: In small bowl, stir together Homemade Salad Dressing, sour cream, mustard, vinegar, sugar, celery seed, salt and pepper; pour over cabbage mixture and toss to coat. (Make-ahead: Cover and refrigerate for up to 2 hours.)
In top of double boiler or in small heavy-bottomed saucepan, whisk together sugar, flour, mustard, salt and turmeric. Whisk in egg yolk, vinegar and milk.
Cook over saucepan of simmering water or over medium-low heat, stirring constantly, until thick enough to coat back of spoon, about 10 minutes. Stir in butter. Let cool, stirring often. (Dressing will continue to thicken as it cools.) (Make-ahead: Scrape into airtight jar, cover and refrigerate for up to 1 week.) [[Makes about 1 cup.]]