preheat oven to 350. spread the walnuts on a baking sheet and bake until lightly toasted, 5-7 minutes. Let cool,then coarsely chop.

make the dressing. whisk the vinegar,mustard,sugar,11/2 tsp of salt and 1/2 tsp pepper in a large bowl. gradually whisk in olive oil until well blended,then whisk in sour cream.

add cabbage,cilantro,tarragon,scalliins,grapes and toasted walnuts to the bowl;toss to coat with dressing. cover and refrigerate 1-4 hours before serving.