Combine the olive oil and white balsamic in a small jar.
Add the dressing to the mixed greens and fennel and toss through. Arrange the greens on one large platter or onto individual plates. Lay the nashi pear on the greens, then using a potato peeler, finely shave the pecorino and sprinkle it onto the salad. Top with pecan nuts and serve.
Note: If peeled, the level of salicylates drops to negligible amounts in the Nashi pear.