Combine kale, broccoli, dried cranberries, and walnuts in a large bowl. Set aside.
Prepare Sweet and Sour Dressing
In a medium bowl, whisk together shallot, white sugar, apple cider vinegar, salt, dry mustard, and celery salt until combined. Slowly pour in vegetable oil while whisking until mixture thickens.
Pour salad dressing over kale mixture and toss, making sure the salad is fully covered.
Cover and refrigerate for 2 hours for best flavor.