Working with only the smallest fresh artichokes, remove tough outer leaves; cut a thin slice off the bottom of the stem, and trim the top of the artichoke, removing the thorns. Cut each artichoke in half lengthwise. Rub all cut areas with lemon to keep artichokes from turning brown. Poach in simmering salted water with the 1/2 lemon, until tender (about 10 minutes). Strain and reserve. Discard lemon. Poach peas in simmering salted water until tender. Strain and reserve. Sauté onion in extra virgin olive oil very slowly, on a very low flame, for about 20 to 30 minutes, or until translucent. Stir four to five times during cooking, taking care not to brown them. Toss artichokes, peas, onions, and mint together and season with salt and pepper. Serve chilled or at room temperature. *If baby artichokes are not available, the next best thing is frozen artichoke hearts. Canned artichoke hearts can also be used, but the flavor and texture will be slightly different.