Feel free to use your favorite mix of greens in this salad. If you want to use arugula and baby kale, by all means go for it. I like to roast a few apples and blend them with the vinegar right in the blender. That way I can make dressing for as many or as few salads as I'm making, and make it right to order. The base keeps in the fridge for a good 2-3 weeks.