Cook the pasta according to the directions on the package. Drain the pasta, rinse it under cold water, and put it in the refrigerator to chill.
In a dry saute pan toast the walnuts over a medium-high flame until they are fragrant, about 2 minutes. Set the walnuts aside to cool then chop them coarsely.
In a large bowl, toss together the chilled pasta, walnuts, feta cheese, onion, and spinach. In a small bowl whisk the oil, vinegar, garlic and mustard. Pour the dressing over the pasta salad and toss to combine. Season with salt and pepper.
2006, Ellie Krieger, All Rights Reserved