How to Make It
Preheat the oven to 400°. Squeeze the lemon juice into a large bowl of cold water. Cut off the artichoke stems. Trim the tops and pull off the tough outer leaves. Halve the artichokes lengthwise, then thinly slice. Drop the artichokes into the acidulated water.
Put the couscous in a heatproof bowl, season with salt and pepper and scatter the butter all over. In a small saucepan, bring the stock to a boil and stir it into the couscous; cover and set aside for about 8 minutes. Fluff the couscous with a fork; it should be soft. If not, add a little hot water.
Meanwhile, in a large nonreactive skillet, heat the 3 tablespoons of oil. Drain the artichokes. Add them to the skillet with the shallots, season with salt and pepper and cook over moderate heat, stirring, until the artichokes are beginning to brown, about 8 minutes. Reduce the heat to moderately low, add 1/2 cup of water and cook until tender, about 4 minutes. Add the artichokes to the couscous and let cool slightly. Add the prosciutto, olives, pine nuts and half the cheese to the couscous. Season with salt and pepper and toss gently.
Cut off the tops of the peppers and scoop out the seeds and ribs. Lightly brush the peppers with oil and fill them with the couscous mixture. Sprinkle the remaining cheese on top. Stand the peppers upright in a 13-by-9-inch baking dish. Pour about 1/2 inch of water into the dish and cover the peppers loosely with aluminum foil. Bake for 30 minutes, or until the peppers are barely tender. Set the reserved tops on the peppers and bake for another 30 minutes, or until the peppers are tender. Serve warm or at room temperature.