Saute onion and carrot in 2 tablespoons butter until soft. Set aside.
In 4 quart saucepan, melt 4 tablespoons butter and add flour, whisking constantly over medium heat until roux becomes light brown (about 5 minutes). DO NOT BURN!
Slowly add seafood stock, whisking constantly to ensure mixture stays smooth.
Add onions and carrots, cover, and simmer for 1/2 hour.
Add cream, sherry, lemon juice, Worcestershire sauce, cayenne pepper, salt, and lobster or crab and simmer an additional 5 to 10 minutes.
Garnish with fresh minced chives, hot chili oil & crab.