To cut the fennel into thin, even slices, use a mandoline. Cut the bulb in half lengthwise, trim off any tough outer layers, then slice the fennel on the mandoline. Inexpensive plastic Japanese and German mandolines work well. We also like the Good Grips Mandoline from Oxo (oxo.com).
Other hard, aged Italian cheeses can be substituted for the Pecorino Toscano. Try the slightly milder, gritty Parmigiano-Reggiano or the sweeter Asiago.