In a small bowl, whisk together the vinegars, mustard and sugar. Add the oil in a stream, whisking, and whisk vinaigrette until emulsified. Stir in the shallot, salt and black pepper.
PREPARE NUTS:
In a small saucepan, melt the butter over moderate heat and add the walnuts and sugar. Cook the walnuts, stirring, until golden, about 2 minutes, and transfer to a bowl.
PREPARE SALAD:
Cut the endives lengthwise into julienne strips. Halve and core the apples and cut into julienne strips.
In a large bowl, combine the endives, apples, walnuts, blue cheese, tarragon and vinaigrette, tossing gently, and season with salt and white pepper.
Notes
I like to buy a wedge of blue cheese for this one and break it into chunks. It's so much more delicious than the package of blue cheese crumbles that you can buy in the store.
If you're counting WW Points, be sure to use reduced fat blue cheese in this delicious salad!