Step 1Pour enough water into a large stockpot to cover the crayfish. Add the salt, sugar, dill, carrot and celery. Over high heat, bring to a boil.
Step 2Add the crayfish; cover and return to a boil. Reduce the heat to a simmer and cook until the crayfish have turned red, about 10 minutes total from the time they are put in the pot. Pull off a tail to check for doneness. Drain; discard the vegetables and allow the crayfish to cool.
Step 3Combine the butter with the jalapeno and cilantro, if desired, and divide it among dipping bowls.
Step 4Transfer the crayfish to a serving platter and garnish with additional dill and lemon wedges. Serve with the butter sauce for dipping.