With a mandoline on the thinnest setting, or with a very sharp knife, shave the Brussel sprouts into 1/8 inch slices. Cut off the top fronds of the fennel and remove the hard outer layer from the bulb.
Using the mandoline or sharp knife, thinly slice the fennel bulb into 1/8 inch slices. Add the shaved Brussel sprouts and fennel to a large salad bowl. Add the spinach, romaine, pomegranate seeds and pear. Toss with some of the dressing.
Let sit for about 15 minutes before serving.