In a small saucepan, bring the balsamic vinegar, shallots, and sugar to a simmer over medium heat. Simmer uncovered, stirring frequently, until liquid is reduced by half, about 8 minutes. Add the preserves and cook 1 more minute.
Transfer the mixture to a blender; add the oil and red wine vinegar and puree until smooth. Season with salt and pepper. Chill.
Place the spinach on a large platter or in a large salad bowl. Add the chicken, strawberries, green onion, cucumber, and pistachio nuts. Drizzle the dressing; toss and serve. You can also plate the salad and then drizzle the dressing on to individiual servings.