Whole stuffed artichokes make an impressive statement at the table and are quite easy to prepare. Here we've added bacon and parmesan cheese to enliven the stuffing. The artichokes steam while cooking in the oven, so it's important to keep an eye on the level of cooking liquid in the pan during the roasting stage.
Position a rack in the lower third of the oven and preheat to 400 degrees F.
Spread the bread crumbs on a baking tray and bake until golden, about 10 minutes. Cool and then transfer the crumbs to a medium bowl.
Meanwhile, place a skillet over medium heat and add the olive oil. When the oil is hot, add the leek and bacon. Cook, stirring frequently, for 3 minutes or until the leeks begin to wilt. Add the garlic and continue cooking for another 3 to 4 minutes, stirring frequently. Remove the pan from the heat and let the mixture cool.
When cool, add the contents of the skillet to the bread crumbs. Stir in the parmesan, lemon zest, and parsley. Season to taste with salt and pepper. Set the stuffing aside at room temperature.
Cut off the stems of the artichokes and discard or save for another use. Cut off the top third of each artichoke and discard. Gently spread the leaves outward from the center of each artichoke to partially open it like a flower. Remove the pointed leaves and hairy choke from the center with a small spoon or melon baller, and discard.
Spoon some of the stuffing into the center of each artichoke, adding stuffing between the leaves as well. Transfer the artichokes to a deep glass or ceramic baking pan, and top each vegetable with a knob of butter. Add enough hot water to come 1/2 inch up the sides of the artichokes. Don't add too much water or the stuffing will get soggy. Cover the pan tightly with a lid or a sheet of aluminum foil.
Transfer the pan to the oven and cook until the artichokes are tender when pierced with a sharp knife or skewer, about 40 minutes. Remove the lid or foil, and continue cooking until the stuffing is golden, 5 to 10 minutes more. Carefully remove the artichokes from the pan with tongs or a slotted spatula, and serve hot or warm.