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, stock, salt, cayenne pepper, and mustard 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 an immersion blender (or in batches using a 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.