Peel the oranges and remove the white pith. Over a bowl positioned to catch the juice, separate the segments of each
orange from the membrane with a sharp knife, discarding the seeds, and set them aside. Squeeze the residual juice from the membranes into the bowl and reserve.
Combine the spinach and watercress in a mixing bowl.
Put the pine nuts (or cashews) in a small sauté pan and cook over medium heat for about 6 minutes, shaking the pan occasionally, until
the nuts are golden brown. Transfer the nuts to a small bowl.
Put the shallots, garlic, vinegars, and reserved orange juice into the sauté pan. Bring to a boil over
low heat. Stir in the black pepper, then pour the dressing over the spinach and watercress. Toss to coat.
Arrange the mixture on salad plates, spoon orange segments on top and garnish with the nuts.