Put the shallot and vinegar in a ramekin, and set aside to macerate.
Cut the fingers off the fennel bulb, and discard, and then peel the bulb. Slice the bulb very thinly into rings. Toss with the mushroom slices, and parsley leaves. Dress the mixture with olive oil, and season with salt, pepper, and lemon juice, to taste. Serve with Parmesan curls on top.