Stir 3 tablespoons of the lemon juice into a bowl of water. Working with 1 artichoke at a time, pull off the dark outer leaves and trim 1/2 inch off the top. Peel the stem. Halve the artichoke, slice it thinly lengthwise and add to the water.
In a large bowl, whisk the shallot into the remaining 2 tablespoons of lemon juice. Whisk in the oil in a thin stream and season with salt and pepper.
Drain the artichokes well and toss them with the dressing. Refrigerate for at least 1 hour or overnight. Season with salt and pepper and garnish with the Parmesan.