Fill a bowl with water, squeeze in the juice from the lemon, and drop in the peel. Trim the artichokes, halve or quarter (depending on size), and drop in the water until ready to use. (If using globe artichokes, cut the trimmed hearts into eights.)
Melt the butter in a sauté pan. Add the bacon and brown it, 5 minutes. Drain the artichokes and add to the pan, along with the carrots and onions. Season with salt and pepper. Pour over the stock. Cover and cook until tender, 7 to 10 minutes. Uncover and add the favas or peas until tender, approx. a minute. (If the liquid is all gone, you could add a splash more stock.) Stir in the crème fraîche. Taste and adjust the seasonings, adding lemon juice to taste. Serve hot, sprinkled with chopped coriander or tarragon for garnish.