Small luxuries like lobster and baby artichokes make this appetizer special enough for any festive occasion.
Fill a large bowl with water. Cut 2 lemons in half; squeeze juice into bowl. Add the squeezed lemon halves. Set aside.
Remove and discard all the leaves from artichokes. Using a sharp knife, trim all traces of dark outer layers from bottoms. Using a melon baller, scoop out and discard the chokes. Transfer the artichoke hearts to the reserved lemon water.
Fill a nonreactive medium saucepan with salted water. Cut the remaining 2 lemons in half; squeeze juice into water; add the squeezed lemon halves. Drain the artichoke hearts, and discard lemon halves. Transfer the artichoke hearts to saucepan. Place a heat-proof bowl over the artichokes, keeping them submerged.
Set saucepan over high heat, and bring the liquid to a boil. Cook hearts until tender, about 8 minutes. Remove pan from heat, and drain hearts. Set aside until cool enough to handle. Cut hearts into 1/4-inch-thick slices. Cover; set aside.
Place wine and 3 cups water in a large stockpot. Add tarragon and 4 lemongrass stalks. Bring liquid to a boil. Add lobsters; cover, and cook over high heat about 8 minutes. Remove lobsters, and transfer to a bowl until cool enough to handle. Carefully remove meat in whole pieces from the tails and claws; set aside. Reserve lobster bodies for another use.
Slice 2 carrots into 1/8-inch-thick rounds, and place in a medium saucepan. Cover with water, and season with salt; bring to a boil. Cook carrots until tender, about 3 minutes. Drain, and set aside.
Place the remaining carrots in a juice extractor, and process, extracting all the juice. Transfer the juice to a medium saucepan. Add the 4 remaining stalks lemongrass, chicken stock, lime juice, curry powder, cinnamon, nutmeg, and cayenne; season with salt. Bring to a simmer; cook 2 minutes. Remove carrot broth from heat; let stand 30 minutes.
Line a sieve with a double layer of cheesecloth; set sieve over a large bowl. Pass cool broth through the sieve; discard solids. Return broth to saucepan. Add the reserved artichoke hearts and the carrot rounds; bring to a simmer.
Meanwhile, bring another saucepan of salted water to a boil. Place the reserved lobster meat in the boiling water, and heat through, about 1 minute. Using a slotted spoon, remove lobster meat from water. Cut tail meat in half lengthwise.
To serve, divide the carrot broth, the vegetables, and the lobster meat among twelve soup plates; garnish with chervil.
To make the carrots look like flowers, use a channel knife to carve grooves along sides.