Set a heavy 4-quart saucepan over medium-high heat. Add the olive oil and butter and once melted, sauté the onion, potato, celery, shallot, Serrano, and garlic until softened and fragrant, about 10 minutes. Add the wine and simmer until the wine is completely absorbed, about 7 - 10 minutes.
Add the celery root, broth, salt, and Old Bay Seasoning in the saucepan and simmer until the celery root is tender, about 35 to 40 minutes.
Remove the saucepan from the heat and puree the soup using a countertop blender or an immersion blender until smooth.Stir in the half-and-half and milk. Taste, and re-season the soup if necessary and garnish with the chervil.
Serve with 3 tablespoons of the sauteed lobster per soup bowl for the meat eaters at the table.
Broiled Lobster Tails
Using kitchen scissors, cut the lobster shells in half, and firmly open up to butterfly the tails. Gently slice through the lobster meat just enough to open it up. Be careful not to cut all the way through the meat.
Melt the butter and stir in the seasoning and salt.
Turn the tails upside down on a broiler pan, and broil for 7 minutes. Flip over and baste with the seasoned butter. Slip back under the broiler for another 4 minutes or until done. Baste again with the season butter.
The lobster tails can be served as is with additional butter alongside the soup, or gently remove the meat from the shells, coarsely chop, and top each bowl of bisque with the meat of one tail.
Notes
The nutrition calculations do not include the optional lobster for the meat eaters.