Take advantage of pears in season and try a new variety in this twist on a popular dish. A little sweet pear (or apple or dried fig) makes the dressing especially good.
Chop 1 pear and slice the remaining 2. Put chopped pear, oil, vinegar, mustard, and honey into a blender and purée. Transfer to a small bowl and stir in 2 tablespoons water, more if needed, to thin for a pourable dressing. Put spinach, onion, walnuts, goat cheese, sliced pears, and dressing into a large bowl and toss gently to coat. Serve immediately.