Use a food processor, mandoline, or sharp knife to shave the Brussels sprouts. Thinly slice the radicchio.
Mix the sprouts, the radicchio, the cranberries, and the pistachios together in a mixing bowl.
Whisk the oil, vinegar, maple syrup, Dijon mustard, and salt together in a small bowl or measuring cup. Toss the dressing over the salad and mix well. Season to taste with additional salt, vinegar, and freshly ground black pepper. Serve.