How to Make It
Squeeze the lemon juice into a large bowl of water. Working with 1 artichoke at a time, snap off the outer leaves and trim off all but 1/2 inch of the stem. Using a sharp knife, cut off the remaining leaves at the top of the heart and peel the base and stem. Using a spoon or a melon baller, scoop out the furry choke. Add the artichoke to the lemon water.
In a large, deep skillet, heat the olive oil. Add the leeks, celery, onion and carrot and cook over low heat, stirring often, until softened but not browned, about 20 minutes. Add the garlic and cook until fragrant, about 1 minute.
Drain the artichokes and add them to the skillet in a single layer. Tuck in the thyme, tarragon and bay leaves and season with salt and pepper. Add the wine and water, cover partially and braise over moderately low heat until tender, about 40 minutes. Discard the herbs.
Meanwhile, blanch the peas, asparagus, fennel and haricots verts separately in boiling salted water until crisp-tender, 5 minutes for the peas and fennel and 3 to 4 minutes for the haricots verts and asparagus. Using a slotted spoon, transfer the vegetables to paper towels to drain after they are cooked.
Mound the peas, asparagus, fennel and haricots verts in soup plates and add some of the braising vegetables and liquid. Season with salt and pepper. Set an artichoke on top and fill with diced tomato. Scatter the mixed herbs over the top and serve warm.