|'French' shallots generally produce large bulbs. Shallots, also called scallions, are generally cultivated like onions. They overwinter in the ground, and actually produce healthier and more plentiful bulbs if they go through this vernalizing experience.
If the stalks flower, cut them down so the plant's energy can be directed to the bulbs. Generally, harvest in midsummer, when the plants wilt or fall over, and store the bulbs in a cool, dry place. Shallots generally harvest a bit earlier than garlic.