How to Make It
Preheat the oven to 350°. Brush the baguette slices with 1 tablespoon of the olive oil, transfer to a baking sheet and toast for 15 minutes, until golden. Let cool, then break the bread into 3/4-inch pieces.
In a large bowl, combine the remaining 3 tablespoons of olive oil with the lemon juice. Add the fennel, arugula, onion, Pecorino cheese and croutons, season with salt and pepper, toss well and serve.
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.